Category: Physic Tutorials

A potential divider circuit is arranged in such a way to get an output voltage from a battery of particular e.m.f.

For a potential divider, the current through the each resistor is the same because they are arranged in series.

Potential Divider derivation

Using Ohms law,

The effective resistance is = R₁ + R₂ 

V_in = IR

I = V_in/ (R₁ + R₂ )

The Voltage across R1 will be,

V₁ = IR₁

Since I = V_in/ (R₁ + R₂ )

V₁ =  V_in/ (R₁ + R₂ ) x R₁

V₁ = R₁/(R₁ + R₂ ) x V_in

For voltage across R₂

V₂ = R₂/(R₁ + R₂ ) x V_in

Uses of Potential divider

The circuits are often used in electronic circuits. They are useful when a sensor is connected to a processing circuits.

Temperature sensor

A common example of a sensing system is a temperature sensor in a thermostat, which uses a thermistor. The thermistor is then used in a potential divider as the diagram below. In the diagram, the potential difference is divided between the resistor and the thermistor. As the temperature rises, the resistance of the thermistor decreases, so the potential difference across it decreases and the potential difference across the resistor increases as the temperature increases.

How to calculate in Potential divider circuits

The first thing that must be done is to write down the formula

V_out = R₂/(R₁ + R₂ ) x V_in

Then look at the question to know what you are asked to calculate.

Example 1

The diagram shows a potential divider circuit. The voltmeter has infinite resistance and the battery has negligible internal resistance.

The variable resistor is set on its maximum resistance of 200 Ω. Calculate the voltmeter reading.

Solution

V = 200 /(200 + 180) x 6

V = (200/380) x 6 = 3.16 v

Example 2

In the circuit shown, X is a variable resistor whose resistance can be changed from 5.0 Ω to 500 Ω. The e.m.f. of the battery is 12.0 V. It has negligible internal resistance.

What is the maximum range of values of potential difference across the output?

A 1.3 V to 11.1 V

B 1.3 V to 12.0 V

C 1.5 V to 11.1 V

D 1.5 V to 12.0 V

Solution

V_out = R₂/(R₁ + R₂ ) x V_in

The minimum resistance in variable resistor is 5Ω

V_out = 5/(5 + 40) x 12 = 1.3 v

The maximum resistance is 500Ω

V_out = 500/(500 + 40) x 12 = 11.1 v

The correct answer is A

Recommended: How to calculate and solve questions on resistivity

In this article, I will define; and give the value of the resistivity of some materials, and how to solve some questions on it.

The resistance R is proportional to the length L and inversely proportional to the cross-sectional area A, with a proportionality factor called the resistivity of the material.

Note: In a metal, resistivity increases with temperature.

The symbol is given below,

The Unit is Ωm

It is important to note that its reciprocal is conductivity.

Difference

Resistivity is a property of a material, independent of the shape and size of the specimen, while resistance depends on the size and shape of the specimen or device, as well as on its resistivity.

It then means that the resistance of a wire depends on resistivity, length, area of the wire. Also resistance depends on the temperature.

Resistivity of some materials at room temperature

Calculation

The parameters you must have to calculate include

• Resistance of the material
• Length of the material
• And the cross-sectional area of the material which is

Few Questions

(1) A wire of 5Ω resistance is drawn out so that its new length is two times the original length. If the resistivity of the wire remains the same and the cross sectional area is halved, the new resistance is

A. 40Ω    B. 20 Ω     C. 10 Ω      D. 5 Ω

(2) A wire P has half the diameter and half the length of a wire Q of similar material. The ratio of the length of the resistance of P to that of Q is?

(3) The resistance of a 5m uniform wire of cross-sectional area 0.2 x 10^-6 is 0.425 ohms. What is the resistivity of the material of the wire?

Answers

Q1

Since the ‘resistivity’ is the same

(R1A1)/(L1) = (R2A2)/(L2)

L2 = 2 X L1, A2 = 0.5 x A1

Then,

(5 X A1)/(L1) =( R2 X 0.5A1)/(2L1)

R2 = (5 X A1 X 2L1) / L1 X 0.5A1 = 10/0.5 = 20 ohms

Q2

Diameter of P = 0.5 x diameter of Q

Length of P = 0.5 x length of Q

‘Resistivity’ of P = ‘Resistivity’ of Q

Cross sectional area =

RpAp/Lp = RqAq/Lq

Rp(dp)²/Lp = Rq(dq)²/Lq

Rp(0.5dq)²/0.5Lq = Rq(dq)²/Lq

0.5Rp = Rq

Rp/Rq = 1/0.5 = 2:1

Q3

‘Resistivity’ = RA/L = (0.425 x 0.2 x 10^-6) / 5 = 1.7 x 10^-8

Recommended: Why Ammeter is connected in series and Voltmeter in parallel

From my experience as a tutor and lecturer of physics, I know that there are some repeated topics in physics that JAMB can’t do without bringing out questions.

So, if you want to pass physics in JAMB and score above 60, you must master these topics and make sure you solve all possible questions on them.

I know that writing physics in the exam isn’t as easy as other subjects, but early preparation can help you build the muscle to score high in it.

Read: Solutions to some JAMB physics past questions

Expected Topics

1. Electric field
2. Expansivity questions
3. Direct current (D.C)
4. Work energy and power
5. Nuclear physics
6. Gas law
7. Current of electricity
8. Alternating current
9. Magnetic field and E.M induction
10. Questions and answers of Machine and light waves
11. Heat energy
12. Capacitance of a capacitor
13. Gravitational field
14. Stationary waves and Diffraction
15. Wave motion
16. moment of a force
17. Kinematics and deformation of solid
18. Measurement
19. Dynamics
20. Friction
21. Dimension Analysis
22. Fundamental and Derived quantities
23. Scalar and Vector quantities

Questions to be expected

The questions below are extracted from JAMB past questions and it is intended to give you an idea of some UTME physics questions that do come out. If you checked 5 – 6 years past questions, you might notice some questions do appear repeatedly.

• Example of vector quantity – velocity, acceleration, moment, displacement, force, electric field intensity, magnetic flux
• Examples of scalar quantity – work, time, mass, distance, energy, pressure, speed, temperature
• The resultant of two forces acting on an object is maximum if the angle between them is – 0^o
• The terrestrial telescope has one extra lens more than the astronomical telescope. The extra lens is for -erection of the image
• What is the angle of dip at the magnetic equator? – 0^o
• At resonance, the phase angle in an a.c. circuit  is – 0^o
• The process of energy production in the sun is – Nuclear fusion
• A transistor functions mainly as a – switch and amplifier
• Energy losses through eddy currents are reduced by using – insulated soft iron wires
• The effect of a particle in a fluid attaining its terminal velocity is that the – weight is equal to the retarding force
• Water is a poor thermometric liquid because it – wet glass
• To produce an enlarged and erect image with a concave mirror, the object must be positioned – between the principal focus and the pole
• The phenomenon that makes sound persist when its source has been removed is known as – reverberation
• The colours seen in soap bubbles are due to – dispersion
• The electromagnetic wave that can produce a heating effect on the environment is – infra-red
• Pure silicon can be converted to a p-type material by adding a controlled amount of – trivalent atoms
• The particle that is responsible for nuclear fission in a nuclear reactor is – neutron
• The carbon-granule microphone works on the principle of change in – resistance
• The phenomenon whereby the water droplets in the atmosphere combine with dust particles in the air to reduce visibility is – fog
• In a semi-conductor junction diode, as the depletion or barrier layer is forward biased, the layer – narrows
• As the pressure of a fluid increases, its viscosity – increases
• To change a d.c dynamo to a.c dynamo – commutator should be replaced with slip rings
• Transverse waves can be distinguished from longitudinal waves using the characteristic of – polarization
• The North pole of a magnet can never be separated from the South pole because of a property known as – magnetic dipole
• The charge carriers in gases are – electrons and ions
• The ray which causes gas molecules to glow is known as – cathode ray
• Lenz’s law is a law of the conservation of – Energy
• The phenomenon of light bending round an obstacle is – diffraction
• The instrument that measures both a.c. and d.c. is – moving iron ammeter
• What is the leat possible error in using a rule graduated in centimeters? – 0.5 cm

For candidates that are requesting for physics guide especially on calculations, click here for preparatory physics guide and download.

• The object moves with uniform speed round a circle. Its acceleration has – constant magnitude and varying direction
• The motion of a moving skin of a talking drum can rightly be described as – oscillatory
• Isotopes are nuclei which has? – the same atomic number but different mass number
• The net charge on the atom is zero because – the neutrons form shield around the charged protons
• Gases conduct electricity under – low pressure and high voltage
• For resonance to occur in a.c circuit containing a resistor, capacitor and inductor – when the frequency source is such that the reactance of the capacitor is equal to the inductive reactance
• In a purely inductive circuit, the current – lags behind the voltage in phase by 90 degree
• The principle of operation of an induction coil is based on – Faraday’s law
• A dynamo primarily converts – mechanical energy into electrical energy
• To convert a milliameter to an ammeter – a low resistance in series is required
• In order to convert a galvanometer into an ammeter – a low resistance shunt is connected in parallel
• If two parallel conductors carry currents flowing in the same direction, the conductors will – attract each other
• A calibrated potentiometer is used to measure the emf of a cell because the – potentiometer takes no current from the cell
• The resistance of an open series circuit is – infinite
• When white light is dispersed by a spectrometer, the component having the shortest wavelength is – violet
• In photo-emission, the number of photoelectrons ejected per second depends on the – Intensity of the beam
• The particle nature of light is demonstrated by the – photoelectric effect
• Capacitors are used in the induction coil to – prevent electric sparks

I hope that I have been able to help you get topics that are likely to come out in JAMB Physics through the UTME Physics past questions. These topics and questions will help you when you are preparing to write your.

I wish you the best. If you have any questions, you can leave a comment below.

Recommended: Download JAMB physics syllabus

Water behaves anomalously when compared with other liquids at certain temperatures. Most liquid expand when heated and contract when cooled. However, at 0^oc and 4^o c anomalous behaviour of water occurs between those ranges of temperature.

When water is heated from 0^oc to 4^o c, it contracts and expands when cooled from 4^oc to 0^o c. But at any other temperature it behaves normal. This anomalous expansion of water makes ponds, lakes or rivers to freeze from the top surface rather from the bottom.

This anomalous behaviour of water also implies that when water is heated from 0^oc to 4^o c the volume decreases while the density increases.

In this range (0^oc and 4^o c), its coefficient of volume expansion is negative. Thus, water has its greatest density at 4^o c. Water also expands when it freezes; that’s why pipes full of water burst if allowed to freeze. Most other materials contract when they freeze.

Mathematically,

Density = mass/volume (the higher the volume the lower the density and vice-versa).

Increase in inter-atomic spacing explains why liquids are generally less dense than solids.

The molecules of liquids have small spacing but with some gaps, less well ordered, and motion fairly slow.

Note: as the temperature of liquid rises from 0^oc to 100^oc, the molecules move increasingly rapidly. Their kinetic energy is increasing. There is very little change in the mean separation between the molecules and therefore very little change in their electrical potential energy.

Questions and Answer

1) At 4⁰C, the volume of a fixed mass of water is

A. constant B. minimum C. maximum D. zero.

Answer

At 4⁰C the volume of water is minimum.

2) If a container is filled with ice to the brim, what happens to the level of water when the ice completely melts?

A. The water in the glass outflows.

B. The level of water drops.

C. The level of water remains unchanged

D. The level of water goes up.

Answer

Option B.

Water expands on solidification (freezing); when this solid melts, it implies the water reduces in volume.

Read:

• How to solve questions on linear expansitivity
• Heat Capacity

These SS1 Physics questions below are followed based on the SS1 Physics scheme of work in Nigeria. And if you have any questions concerning any of the questions, kindly leave a comment.

Measurement

1)Which of the following shows the correct derived unit for volume?

a) M^4   b) M^-2       c) M^3         d) M^-1

2)  Which of the following is not Basic unit?

a) m        b)NM      c) kg     d) k

3)  Which of the following is a fundamental quantity?

a) Pressure    b) heat    c) luminous intensity   d) Density

4)  The following are Derived units except

a) kgms-2    b) Mol.     c) Nm      d) ms-2

5) The following are instruments used to measure time except

a) stop-watch   b) pendulum clock   c) wattmeter   d) ticker tape timer

6) Which of the following prove the correctness of velocity using the dimensional analysis.

a) LT^-1       b)L^-1T       c)LT^-2    d)LT^-3

Position

1)Which of the following is correct?

i)Displacement is a scalar quantity

ii) Both distance and displacement are measured in meter (m).

iii) Displacement shows direction.

a) i and ii    b) ii and iii     c) i, ii, iii       d) i and iii

2)  What is the distance between point D(9,6) and point F(5,3)

a) -5    b) -15        c) 5       d) 15

3)  Which of these can be used to measure the direction of motion of the body except?

a) Compass     b) Grid         c) Calipers       d) Protractor

4)  Which of the following is not correct about displacement?

a) Displacement is a scalar quantity.

b) Displacement direction can be measured using compass and grid.

c) Displacement is distance moved in a specified direction.

d) Distance has direction while displacement has magnitude only.

5)  Which of the following statements is correct?

i) Distance and displacement have magnitude.

ii) Distance has direction and displacement has magnitude only.

iii) They are both measured in meters.

a) I and iii    b) ii and iii        c) i, ii and iv       d) i, iv, and iii

motion

1)The motion of the prongs of a sounding turning fork is

a) Vibration   b) translation  c)random  d) vibratory and rotational

2)  Which of the following is not true about motion?

a) Motion are caused by a force

b) Motion is the change of position of a body with time

c) All motion are relative motion

d) It is not practicable for an object to combine two of the motion together

3)  Which of the following are random motions?

i) It is haphazardly or disorderly with no direction

ii) It is non-linear manner and changes direction continuously.

iii) Brownian motion is a random motion.

iii) The example of random is a horse running from one two to another

a) I, II& IV only    b) I, II & III only    c) IV, III and I    d) IV, III and II only

4)  A fully test-tube that floats upright in the water is carefully and slightly depressed, and the then released. Which of the following best explains the subsequent motion of the test tube?

a) Rotational   b) Translational      c) Circular     d) Random

5)  A proof of the particle nature of matter is the

a) Oscillatory   b) Brownian motion      c) Orbital motion     d) Translational motion

speed and velocity

1)An object moves with uniform speed around a circle. Its acceleration has:

(a) Varying magnitude and varying direction

(b) Constant magnitude and constant direction

(c) Varying magnitude and constant direction

(d) Constant magnitude and varying direction

2)  The frictional force between two bodies

(a) Have all these characteristics

(b) Exists only when there is relative motion or tendency to motion.

(c) Acts so as to oppose the motion.

(d) Depends on the proper reaction between the two surfaces.

3)  A wooden block of mass 1.4kg rests on a rough horizontal surface. If the surface is 9N, calculate the coefficient of friction g = 10m/s2

(a) 0.65  (b) 0.54  (c) 0.64  (d) 0.70

4)  Which of the following correctly gives the relationship between linear speed and angular speed w of a body moving uniformly in a circle of radius r?

(a) v = w^2r  (b) v = wr^2  (c) v = w /r (d) v = wr

5)  The magnitude of the force required to make an object of mass m move with speed v in a circular path of radius r is given by the expression

(a) mv^2/r  (b) mr2/v  (c) mv/r^2   (d) mv/r

6)  Which of the following is not a consequence of a force field?

(a) Magnetic force  (b) gravitational pull c) electric force  d) surface tension

7)  Which of the following is not correct about friction?

a) friction can be increased using volleys, lubricants

b) friction resists the resistance motion between two surfaces in contact

c) it reduces the efficiency of machines

d) the coefficient of friction has no unit

8)  What is the unit of frictional force?

a) Rad/sec b) Newton  c) N/S   d)  radian

9)  Which of the following are contact forces?

(i) Force of tension   (ii) Force of reaction   (iii) Force of friction (iv) Magnetic force

(A) i, ii and iv only    (B) i, ii and iii only   (C) ii iii and iv only (D) i, ii only.

10)  A body at the weight of 100N moves with a speed of 5mls in a horizontal circular path of the radius. Calculate the magnitude of the centripetal force acting on the body g = 10m/s2

(A) 50N    (B) 100N   (C) 75N   (D) 10N

11)  The area under the curve of a velocity-time graph represents.

(A) Instantaneous speed   (B) Time spent (C) Distance   (D) Acceleration

12)  Which of the following statement is correct about speed and velocity?

(A) Velocity relates to translational motion while speed relates to circular motion

(B) Speed and velocity have the same units

(C) Velocity and speed cannot be represented graphically

(D) Speed and velocity are vector quantities

13)  14)The distance travelled by train may be calculated from the area under its

(A) Distance – graph

(B) Acceleration – time graph

(C) Displacement – time graph

(D) Velocity – time graph

14)  A body accelerates uniformly from rest at 2m/s². Find its velocity after travelling 9m.

(A) 4.5m/s  (B) 24m/s  (C) 6m/s  (D) 16m/s

Rectilinear Acceleration

1)A crate is pulled a distanced along a smooth horizontal floor by a force of magnitude F, Inclined to the horizontal at an angle O. The work done is.

a) F d sin        b) Fd sec           c)Fd Cos            d)Fd Cosec.

2)  Which of the following units has the same unit as the watt?

a) Force x velocity       b) Force x time                  c) force x distance           d) force x acceleration

3)  An object of mass 60kg is released from the height of 3m from the height of 3m. Find the kinetic energy just before it strikes the ground (g =10mls2.

(a) 1.8 J                (b)180J                 (c)18000J            (d)1800J

4)  A stone of mass mkg is held h meters above the floor for 40s. The work done in Joules over this period is

(a)mgh                   (b)O                       (c)mgh/40                           (d)mg

5)  Under which of the following conditions is a work done

a) A bag of Cocoa stands on a platform

b) A woman holds a pot of water

c) A girl climbs onto a table

d) A man pushes against a stationary petrol tanker

6)  Power is defined as the:

a) Product of force and distance

b) Ability to do work

c) Capacity to extort a force

d) Energy expanded per unit time

7) A man of mass 60kg ascends a flight of stairs 5m high in 5 seconds. If the acceleration due to gravity is 10m/s², the power expended is?

a) 600w  b) 0w  c) 60w  d) 0.60w

Heat Energy

1) A wire, 20m long is heated from a temperature of 50^oC to 55^oC. If the change in length is 0.030m, find the linear expansion of the wire.

(a) 3.0 x 10^-3K^-1  (b) 3 x 10^-5K^-1      (c) 0.3 x 10^-5K^-1   (d) 1 x 10^-5K^-1

2)  The linear expansion of a metal P is twice that of another metal T. when these materials are heated to the same temperature change, their increase in length is the same. Find the ratio of the original length of P and T.

(a) 1:4   (b) 2:1        (c) 1:2       (d) 4:1

3)  A uniform capillary tube of negligible expansion, sealed at one end, contains air trapped in a pellet of mercury. The trapped air column is 13.7cm long at 0^oC and 18.7cm long at 100^oC. Calculate the cubic expansion of the air at constant pressure.

(a) 3.65 x 10^-3K^-1 (b) 5.36 x 10^-3K^-1 (c) 3.56 x 10^-3K^-1   (d) 5.63 x 10^-3K^-1

4)  The heat from a fire in a closed room reaches someone far away in the room mainly by

(a) Conduction  (b) Diffusion       (c) Convection   (d) Radiation

5)  Heat transfer by convection in a liquid is due to the

a) Expansion of the liquid as it is heated

b) Ability of the liquid to evaporate at all temperature

c) Translational motion of the molecules of the liquid

d) Increased vibration of the molecules of the liquid about their mean

6)  Which of the following phenomena cannot be explained by the molecular theory of matter?

(a) Expansion       (b) Radiation (c) Conduction (d) Convection

Electric Charges

1)If the leaves of a positively charged electroscope collapse completely as an object is brought near the cap of the electroscope, the object possess:

a) An equal amount of positive charge

b) Less amount of negative charge

c) A positive charge

d) An equal amount of negative charge

2)  A short chain is usually attached to the back of a petrol tanker trailing behind it to ensure that the

(a) Chain provides sound for the resonance of the tanker’s engine

(b) Heat generated by friction in the engine can be conducted to the floor

(C) Charges generated by friction in the tanker is conducted to the earth

(d) Tanker moves slowly as the chain touches the road

3)  Which of the following instrument can be used to compare the relative magnitudes of charge on two given bodies? (a) Proof planes (b) Gold Leaf electroscope (c) The Ebonite rod (d) The electrophorus

4)  A negatively charged rod is brought near the cap of a gold-leaf electroscope. The cap is earthed momentarily while the rod is near to it. The rod is then removed. Which of the following is correct?

a) The cap will be positively charged and the negatively charged leaves will diverge

b) The cap and the leaves will be positively charged

c) The leaves will not diverge because the cap has been earthed

d) The cap and leaves will be negatively charged.

Electric field is a region of space where a charge experience a force. In this article, I will be providing solution to some electric field examples.

Example 1

Which diagram correctly shows the electric field between two charged plates?

the electric field lines between two parallel plates are

• parallel
• equally space
• curve at the edge which is know as edge effect
• the field lines moves from the positive plate to the negative plate

From the above condition, option C is the right answer.

Example 2

The diagram shows two parallel, charged plates.

Which statement about the electric field at points P, Q and R is correct?
A The field at P is greater than the field at Q and R.
B The field at P is less than the field at Q and R.
C The fields at P and Q are equal but greater than the field at R.
D The fields at all points P, Q and R are all equal.

Answer

Kindly note that the electric field in the above diagram is a uniform electric field i.e. the field that exist between two parallel charged plates.

This then means that the electric field strength at any point in the field is the same. Option D is right.

Example 3

There is a potential difference of 200 V across a pair of parallel plates which are 4.00 cm apart. Calculate the force on a charge of 2.50 nC which is between the plates.

The electric field strength formula = V/d, also, E =f/q

V is the potential difference across the plate

d is the distance between the plate

f is the force on the charge

q is the charge

equating the two formulas,

f/q = v/d

f = vq/d = 200*2.5*10^-9/4*10^-2= 125*10^-6 N = 1.25*10^-5N

Example 4

An isolated metal sphere A of radius 26 cm is positively charged. Sphere A is shown in Fig below.

Electrical breakdown (a spark) occurs when the electric field strength at the surface of the sphere exceeds 2.0 × 10^4 V m–1. Calculate the maximum charge Q that can be stored on the sphere. (CIE Physics may/june 2018 P41)

Answer

E = Q/(4*pi*permitivity*r^2)

Q = 20000*4*3.142*8.85*10^-12*0.26^2

Q = charge = 1.5 × 10^–7C

Example 5

A particle has a charge of +2.0 mC and is in a vertical uniform electric field. An electric force of 1.0 × 10–2N acts upwards on the particle. What is the electric field strength?
A 0.20 V m–1 downwards
B 0.20 V m–1 upwards
C 5.0 V m–1 downwards
D 5.0 V m–1 upwards

Answer

Electric field formula = Force/Charge = F/Q = 0.01/0.002 = 5.0 Vm-1. The charge is positive and the electric force acting on the charge act upward i.e moves toward the negative plate. This then means the electric field strength with move upward.. D is the answer

Recommended: Note on electric field

Many of the most important applications of capacitors depend on their ability to store energy and not accumulate and store charges. It just separates an equal amount of charges on either plate and keeps them there, storing potential energy by doing so.

When a capacitor is connected to a battery, electrons flow from the negative terminal of the battery onto the plate A of the capacitor connected to it. At the same rate, electrons flow from the other plate B of the capacitor towards the positive terminal of the battery. Positive and negative charges thus appear on the plates, and oppose the flow of electrons which cause them.

Due to voltage at the two ends of the capacitor, there is an electric field between the two plates, and this electric field keeps (or separate) the charges in their position.

The energy is stored in an electric field between the plates.

The electric potential energy stored in a charged capacitor is just equal to the amount of work required to charge it—that is, to separate opposite charges and place them on different conductors.

In summary

• Capacitor has equal magnitude of +ve and -ve charge
• Total charge on capacitor is zero or no resultant charge
• Energy stored because there is charge separation

Recommended: Notes on Capacitance of a capacitor

Below are few of the soluions to CIE physics 2015, 2016 and 2018 may/june Paper 1 questions.

Question 1

What is a unit for stress?

Solution

Stress = Force/Area = (Mass x acceleration)/(length x length) = Kgms^-2/m^2 = kgm^-1s^-2

Question 2

Physical quantities can be classed as vectors or as scalars. Which pair of quantities consists of two vectors?

A kinetic energy and force

B momentum and time

C velocity and electric field strength

D weight and temperature

Velocity and Electric field strength are both vector quantities.  C is the correct answer

Question 3

Two dogs pull a sledge along an icy track, as shown.

Dog X pulls with a force of 200 N at an angle of 65° to the front edge of the sledge. Dog Y pulls with a force of 120 N at an angle of 45° to the front edge of the sledge. What is the resultant forward force on the sledge exerted by the two dogs?

A 80 N    B 170 N      C 270 N        D 320 N

Dog X with force 200N at an angle of 65

Let resolve into vertical and horizontal component (resolution of forces)

Horizontal component = 200 sin 65 = 181.2615

Vertical component = 200 cos 65 = 84.5236

Dog Y with force 120N at an angle of 45 to the front of the sledge

Vertical component = 120 cos 45 = 84.8528

Horizontal component = 120 sin 45 = 84.8528

Sum of the vertical forces = Vx – Vy ( Vx is in opposite direction to Vy, the reason for the negative sign) =  84.5236 – 84.8528 = -0.3292 N

Sum of the horizontal forces = Hx + Hy (same direction) = 181.2615 + 84.8528 = 266.1143 N

C is the correct answer

Question 4

The graph shown is that of resistance R of the thermistor (not current) against temperature T.

Solution

Ohm’s law: V = IR

Current I = V / R. So, the current is inversely proportional to the resistance R. The ammeter measures the current, not the resistance in a circuit.

The resistance falls rapidly with temperature at low temperatures, so the current will rise rapidly at low temperatures. Therefore, we need a larger region of the scale to represent a fixed amount of change in current at low temperatures. If the values on the scales are close to each other, the change in readings may not be noticeable.

The resistance curve becomes flatter at higher temperatures, so the current will change more slowly with temperature. Therefore, to represent this region of large temperature, a relatively smaller region of the scale is required. So, the values of the scale can be closer to each other.

A is the correct answer

Question 7

The graph shows the variation with mass of the weight of objects on a particular planet.

What is the value of the acceleration of free fall on the planet?

Solution

acceleration = gradient of the graph = dw/dm (taking the gradient at any point will give the same answer)

(3.2 – 0) /(2 – 0) = 3.2/2 = 1.6 ms-2

B is the correct answer

A 0.63 m s–2     B 1.6 m s–2       C 3.2 m s–2       D 9.8 m s–2

Question 10

A horizontal metal bar PQ of length 50.0 cm is hinged at end P. The diagram shows the metal bar viewed from above.

Two forces of 16.0 N and 5.0 N are in the horizontal plane and act on end Q as shown in the diagram.

What is the total moment about P due to the two forces?

Solution

Since forc 16N is acting at an angle which 30 then there is a need to do resolve the force. In this case to the vertical component.

Fv = 16 sin 30 = 8N (acting upward)

Note 5N is acting downward

The total force = 8N – 5N = 3N. The reason for the subtraction is because they acted in opposite direction

total moment about P = 3 x 50/100 = 1.5Nm

A 1.5 N m    B 4.4 N m      C 6.5 N m        D 9.4 N m

Question 13

Liquids X and Y are stored in large open tanks. Liquid X has a density of 800 kg m–3 and liquid Y has a density of 1200 kg m–3.

At which depths are the pressures equal?

Solution

If pressurea are equal, then

Px = Py

hdgx =hdgy

acceleration of free fall is the same for the two liquid

800*hx = 1200*hy

2hx = 3hy

hx =1.5hy

this means that if hy = 10, then hx = 15

C is the right answer

Question 29

A charged particle is in the electric field between two horizontal metal plates connected to a battery, as shown. There is a force F on the particle due to the electric field.

The separation of the plates is doubled.

What is the new force on the particle?

A F/4      B F/2        C F      D 2F

Solution

Electric field between two parallel plates is an example of uniform electric field, meaning electric field strength is the same at any point in the field.

E = v/d = f/q

f = vq/d, q = fd/v

f1d1/v = f2d2/v

since the potential difference is the same

f1d1 = f2d2

d2 = 2* d1

f2 = f1/2, this means the force will be halved

B is the right answer

Question 39

How many down quarks are in a nucleus of hydrogen-3, 3H1 ?

A 2    B 3     C 4      D 5

Solution

The the nuclues of hydrogen-3, there are 1 proton and 2 neutron

Proton has (UUD) i.e. two up quarks and one down quarks

Neutron has (UDD) i.e. one up quarks and two down quarks

therefore, nucleus of hydrogen -3 = 1*(UUD) + 2*(UDD) = UUUUDDDDD

So there are five down quarks

D is the answer

If you need answers to any CIE Physics A level past questions especially P1, leave a comment.

Solutions to Cambridge A level (CIE) Physics Oct/Nov 2016 P1

The solutions below are guidlines to some topics I felt students want to see their solutions in cambridge A level Oct/Nov 2016 P11. You can comment below to ask any question you may find difficult in Oct/Nov 2016 P11, 12, and 13.

Question 1

The force F between two point charges q1 and q2, a distance r apart, is given by the equation

where k is a constant.

What are the SI base units of k ? {Cambridge A level oct/nov 2016, ques 2, p11}

Solution

The SI base unit of force is Kgms-2

Charge q1 is As

Charge q2 is As

distance r is m

SI base unit of k = (Kgms-2 x m) / (As x As) = Kgm2s-4A-2 (B is the correct option)

Question 2

A student uses a cathode-ray oscilloscope (c.r.o.) to measure the period of a signal. She sets the time-base of the c.r.o. to 5 ms cm–1 and observes the trace illustrated below. The trace has a length of 10.0 cm.

What is the period of the signal? {Cambridge A level oct/nov 2016, ques 5, p11}

Solution

From the graph there are 3.5 oscillations

The distance to cover one oscillations = 10/3.5 cm

Since the time-base of the c.r.o is 5 ms cm–1

The period of the signal = (10/3.5) x 5 = 14.3 ms = 1.4 x 10-2 s (D is the correct option)

Question 3

A cyclist pedals along a raised horizontal track. At the end of the track, he travels horizontally into the air and onto a track that is vertically 2.0 m lower.

The cyclist travels a horizontal distance of 6.0 m in the air. Air resistance is negligible.

What is the horizontal velocity v of the cyclist at the end of the higher track? {Cambridge A level oct/nov 2016, ques 6, p11}

Solution

There are important points to note in this question:

The horizontal velocity v is used to calculate the horizontal distance

The time to reach the maximum height is the time to travel the horizontal distance

At maximum height u = 0

Using H = ut + 1/2gt2

2 = 0 + 1/2×9.81xt2

(t=0.6395s)

Horizontal distance = horizontal velocity(v) x time(t)

6 = 0.6395v

V = 9.4ms-2 (B is the correct option)

Question 4

A car is travelling at constant velocity. At time t = 0, the driver of the car sees an obstacle in the

road and then brakes to a halt. The graph shows the variation with t of the velocity of the car.

How far does the car travel in the 5.0 s after the driver sees the obstacle? {Cambridge A level oct/nov 2016, ques 8, p11}

Solution

The distance travelled by the car = 20 x 0.8 + ½ x 20 x(5 – 0.8) =16 +42 = 58m (C is the correct option)

Question 5

A car has mass m. A person needs to push the car with force F in order to give the car acceleration a. The person needs to push the car with force 2F in order to give the car acceleration 3a.

Which expression gives the constant resistive force opposing the motion of the car? {Cambridge A level oct/nov 2016, ques 11, p11}

Solution

Resultant force = applied force – resistive force

Ma = F- R

R = F- ma —-i

3ma = 2F – R

R = 2F – 3ma —–ii

Substitute for R in eq i

2F – 3ma = F – ma

F = 2ma

Therefore, R = 2ma – ma = ma

Resistive force = ma (A is the correct option)

Question 6

A car travels at a constant speed of 25 m s–1 up a slope. The wheels driven by the engine exert a forward force of 3000 N. There is a drag force due to air resistance and friction of 2100 N. The weight of the car has a component down the slope of 900 N.

What is the rate at which thermal energy is dissipated? {Cambridge A level oct/nov 2016, ques 20, p12}

Solution

Rate at which thermal energy is dissipated = power loss

Power = force x velocity

Rate at which thermal energy is dissipated = drag force x velocity = 25 x 2100 = 5.3 x 104 W (C is the correct option)

Question 7

Two parallel circular metal plates X and Y, each of diameter 18 cm, have a separation of 9.0 cm. A potential difference of 9.0 V is applied between them.

Point P is 6.0 cm from the surface of plate X and 3.0 cm from the surface of plate Y.

What is the electric field strength at P? {Cambridge A level oct/nov 2016, ques 30, p12}

Solution

The kind of field in this this is a uniform electric field. Therefore, at any point in the field the electric field strength is constant.

Electric field strength = potential difference / distance between the plate = 9 / 0.09

Electric field strength at P = 100 Nc-1 (B is the correct option)

You may like to download: Click here to download CIE A Level Physics Past papers 1 Solutions and E-book

Solutions to Cambridge A level (CIE) June 2015 and 2016 physics 9702

I took some questions out of 2015 and 2016 May/June Cambridge A level physics paper 11 and provid solutions to them based on their difficulty level. However, if you have any questions that you need additional explanation in 2015 and 2016 past papers, kindly comment below.

Question 1

The average kinetic energy E of a gas molecule is given by the equation E = 3/2 kT where T is the absolute (kelvin) temperature.
What are the SI base units of k ?
A kg–1m–1s2K          B kg–1m–2s2K         C kg m s–2K–1          D kg m2s–2K–1

Solution

The S.I base unit of Kinetic energy = Kgm2s-2

For temperature = K

K = E/T = kgm2s-2 / k

K = kgm2s-2k-1

D is the correct option

Question 2

A uranium-238 nucleus, 238U92 , undergoes nuclear decays to form uranium-234, 234U92 .Which series of decays could give this result?
A emission of four β-particles
B emission of four γ-rays
C emission of one α-particle and two β-particles
D emission of two α-particles and eight β-particles

Solution

alpha emission  = 4He2

beta emission = 0e-1

For nucleon number and proton number to be conserved Uranium-238 must undergo one α-particle and two β-particles

C is the correct option

Question 3

A cell of e.m.f. 2.0 V and negligible internal resistance is connected to a network of resistors as shown.

What is the current I ?
A 0.25 A             B 0.33 A                  C 0.50 A                   D 1.5 A

Solutiothe two 4 ohms are in parallel

effective resistance is 1/R = 1/4 + 1/4

1/R = 2/4

R = 2 ohms

This 2 ohms is in series with the second 2 ohms

R = 2 + 2 = 4 ohms

This 4 ohms is in parallel with the 2 ohms above, therefore the same E.m.f flows through them

For the effective resistance of 4 ohms

E = IR

2 = I*4

I = 1/2 A

2 ohms and the two 4 ohms are in series, the same current will flow through them

The current that will flow through the 4 ohms = half of 1/2 = 1/4 = 0.25 A

A is the correct option

Question 4

A charged oil drop of mass m, with n excess electrons, is held stationary in the uniform electric field between two horizontal plates separated by a distance d.

The voltage between the plates is V, the elementary charge is e and the acceleration of free fall is g.
What is the value of n ?

A eV/mgd    B mgd/ev       C meV/gd      D gd/mev

Solution

Electric field intensity = F/ne = V/d

F = mg

mg/ne = V/d

mgd = neV

n = mgd /eV

B is the correct answer

Question 5

A sound wave has a speed of 330 m s–1 and a frequency of 50 Hz. What is a possible distance between two points on the wave that have a phase difference of 60°?
A 0.03 m               B 1.1 m                    C 2.2 m                          D 6.6 m

Solution

V = fλ

330 = 50*λ

λ = 330/50 = 6.6 m

phase angle = 2πx/λ

π in rad = 180

60 = π/3

π/3 = 2πx/λ

λ = 6x

6x = 6.6

x = 1.1 m

B is the correct answer

Question 6

A fisherman lifts a fish of mass 250 g from rest through a vertical height of 1.8 m. The fish gains a speed of 1.1 m s–1.
What is the energy gained by the fish?
A 0.15 J          B 4.3 J           C 4.4 J            D 4.6 J

Solution

P.E = mgh = 0.25*1.8*9.81 = 4.415 J

K.E = 1/2 mv2 = 1/2 * 0.25 *1.1^2 = 0.15 J

Energy gained by the fish = P.E +K.E = 4.4 + 0.15 = 4.6 J

D is the correct answer

Solutions to some questions in Cambridge A level May/June 2016 physics P11

Question 1

A car accelerates uniformly from velocity u to velocity v in time t.

On the graph, which area equals the distance travelled by the car in time t ?
A NPTU + PQST      B NPW V + VRSU        C NPW V + WRST          D PST + PQS

Solution

The distance covered by the car is NPSU which is a trapezium. The area under it will give the distance covered. In the trapezium there are three full boxes. The only option that gives three full boxes is option B.

Question 2

Two cars X and Y are positioned as shown at time t = 0. They are travelling in the same direction. X is 50 m behind Y and has a constant velocity of 30 m s–1. Y has a constant velocity of 20 m s–1.

What is the value of t when X is level with Y?
A 1.0 s                 B 1.7 s                       C 2.5 s                             D 5.0 s

Solution

The time X will be at the same dstance with car Y is t

the distance covered for car X is

50 + s = 30t

the distance covered for car Y is

s = 20t

50 + 20t = 30t

50 = 10t

t = 5s

D is the correct option

Question 3

Two spheres approach each other along the same straight line. Their speeds are u1 and u2 before they collide. After the collision, the spheres separate with speeds v1 and v2 in the directions shown below.

The collision is perfectly elastic. Which equation must be correct?
A u1 – u2 = v2 + v1
B u1 – u2 = v2 – v1
C u1 + u2 = v2 + v1
D u1 + u2 = v2 – v1

Solution

relative speed of approach = relative speed of separation for perfectly elastic collision

u1 + u2 = v2 – v1

D is the correct answer

Question 4

The diagram shows a man standing on a platform that is attached to a flexible pipe. Water is pumped through the pipe so that the man and platform remain at a constant height.

The resultant vertical force on the platform is zero. The combined mass of the man and platform is 96 kg. The mass of water that is discharged vertically downwards from the platform each second is 40 kg. What is the speed of the water leaving the platform?
A 2.4 m s–1         B 6.9 m s–1          C 24 m s–1              D 47 m s–1

Solution

The force exerted by the man and the platform = the vertical downward force of the water

96*9.81 = m * v/t

96 * 9.81 = m/t * v

v = 96*9.81 / 40 = 23.544 = 24ms-1

C is the correct option

Question 5

A solid metal cylinder stands on a horizontal surface, as shown.

The cylinder has length x and cross-sectional area A. The cylinder exerts a pressure p on the surface. The acceleration of free fall is g. Which expression gives the density of the metal of the cylinder?
A gx/p                                             B p/gx                              C gx/pA                    D pA/gx

Solution

pressure = force / area

area = A

P = F / A

F = PA

mass = force/acceleration of free fall

mass = PA / g

density = mass / volume

volume = A *x = Ax

density =( PA/g)/Ax = P /gx

B is the correct option

Question 6

A trailer of weight 30 kN is attached to a cab at X, as shown in the diagram.

What is the upward force exerted at X by the cab on the trailer?
A 3 kN                        B 15 kN                           C 30 kN                                D 60 kN

Solution

F * 20 = 30 * 10

F = 300 / 20 = 15 KN

B is the correct answer

Question 7

Some gas in a cylinder is supplied with thermal energy q. The gas does useful work in expanding at constant pressure p from volume V0 to volume VF, as shown.

Which expression gives the efficiency of this change?

A pV0 / q                    B. Vf / Voq                   C. p(Vf – V0 ) / q          D.(Vf – V0 )/V0q

Solution

Efficiency = workoutput / workinput

workinput = q

workoutput = p ( Vf – V0)

efficiency = p ( Vf – V0) /q

C is the correct option

Question 8

Two copper wires of equal length are connected in parallel. A potential difference is applied across the ends of this parallel arrangement. Wire S has a diameter of 3.0 mm. Wire T has a diameter of 1.5 mm.

What is the value of the ratio current in T/ current in S?

A. 1/4  B. 1/2  C. 2  D. 4

Solution

Resistance = (resistivity x length)/Area

Area = (pi x square of diameter)/4

length and resistivity is constant

meaning, Rs(ds)^2 = RT(dT)^2

RS/RT = (dS)^2/(dT)^2 = (3×3)/(1.5×1.5) = 4

Since the wires are connected in parallel, it means that the potential difference across each wire will be the same.

V = IR

IsRs = ItRt

It/Is = Rs / Rt = 4

i.e. the ratio current in T/ current in S = 4

D is the correct answer

Kirchhoff extended Ohm’s law to networks, and gave two laws, which enable current in any part of the network to be calculated.

Kirchhoff’s first law

In a circuit, current may divide up where circuit splits into two separate branches. This doesn’t mean that current will disappear or an extra current will show up from nowhere. This is the basis for Kirchhoff’s first law.

Kirchhoff’s first law states that the current entering any point in a circuit is equal to the sum of the currents leaving the same point. Said differently, the algebraic sum of the currents into any junction is zero.

This law is also called Kirchhoff’s current law. It is an expression of conservation of charge i.e. the amount of charge entering a point must leave the same point. Kirchhoff’s first law obeys principle of conservation of charge.

Kirchhoff’s second law

This law deals with electromotive force (e.m.f.s) and the voltages in a circuit.

Kirchhoff’s second law states that the sum of e.m.f.s around any loop in a circuit is equal to the sum of the p.d.s (potential difference) around the loop.

Kirchhoff’s second law is a consequence of the principle of conservation of energy i.e. energy gain passing through sources of e.m.f = energy lost passing through components with p.d.s. Kirchhoff’s second law obeys principle of conservation of energy.

Kirchhoff’s Applications (Examples)

Ex 1

The diagram shows a junction in a circuit. What is the current Y ?

A +0.2 A

B −0.2 A

C +1.8 A

D −1.8 A

Solution

Current flowing to th point = Current leaving the point

3 + 0.4 = 2.2 + Y + 1.4

3.4 = 3.6 + Y

Y = 3.4 – 3.6 =- 0.2 A

Ex 2

Use Kirchhoff’s laws to determine the currents I1, I2 and I3 in the circuit on the right.

Solution

I2 + I3 = I1 (obeying Kirchhoff’s first law)

Using Kirchhoff’s second law to solve the loop

Ist loop (Clockwise direction)

3 = 10 * I1 +20*I2  (eq 1)

2nd loop (anti-clockwise direction)

1.5 = 20* I2 (eq 2)

I2 = 1.5/20 = 0.075 A

subtituting I2 in eq 1

3 = 10*I1 + 1.5

1.5 = 10* I1

I1 = 0.15 A

I2 + I3 = I1

0.075 + I3 = 0.15

I3 = 0.15 – 0.075 = 0.075 A

Recommended: Note on Direct Current

Note on Alternating current