Free KCSE Physics Topical Questions KNEC Standards - ATIKA SCHOOL

K.C.S.E Physics Q & A - MODEL 2018PP2QN19

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP2QN19

Figure 8 shows two waves of nearly equal frequency produced simultaneously.

On the space provided, sketch the resultant of the two waves (beats).
(b) Figure 9(a) and 9(b) show barriers placed in the path of plane waves.

On each figure, sketch the pattern of waves after they pass the barrier.
(c) Figure 10 shows a displacement—distance graph for a certain wave motion.

(i) Indicate on the figure with letters A and B any two points that are in phase.
(ii) Determine the:
(I) amplitude of the wave
(II) wavelength of the wave
(iii) Given that the frequency of the waves is 50 Hz, determine the:
(I) period
(II) speed of the wave

answers

K.C.S.E Physics Q & A - MODEL 2018PP2QN18

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP2QN18

(a) (i) Draw a circuit diagram showing the depletion layer of a p—n junction diode connected in the reverse bias mode.
(ii) State the reason why increasing the external voltage in (i) makes the depletion layer wider.
(iii) State the meaning of breakdown voltage of a junction diode.
(iv) State one application of diodes.
(b) Figure 7 shows the output on a screen of a CR0 when an a.c. signal is connected to the Y-plates with the time base on.

(i) Given that the time control is 5 ms per division and the y-gain is 100 V per division determine the:
(I) frequency of the ac. signal
(II) peak voltage of the input signal
(ii) State the adjustment that may be made in order to halve the frequency of the a.c. signal.

answers

(ii) The holes and the electrons in their respective regions are attracted away from the junction by the external voltage.
(iii) The voltage at which the diode begins to conduct in the reverse bias mode.
(iv) In rectification circuits for changing a.c. to d. c.
In control of voltages of Zener diode.

(iii) Double the time control to 10ms per division.
Adjust the frequency of the source to half the value

K.C.S.E Physics Q & A - MODEL 2018PP2QN17

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP2QN17

(a) Water waves from a certain Source move from the shallow end to the deep end. State the change that occurs at the deep end on the following:
(i) Frequency
(ii) Wavelength
(iii) Velocity

(b) (i) A biconvex lens forms an upright image twice the size of the object. If the focal length of the lens is 20cm, determine the object distance.
(ii) State two optical instruments which produce a magnified real image using a Convex lens.
(c) State one difference between the working of the human eye and the lens of a camera.
(d) A lens of focal length 2Ocm forms a virtual image when an object is placed 60cm from the lens. State with a reason the type of lens used.

answers

(a)(i) No change in frequency
(ii) Wavelength increases
(iii) Velocity increases

(ii) a film projector
A compound microscope
(c) In a camera focusing is done by changing the distance between the lens and the film. While in the eye focusing is done by changing the curvature of the lens.
d) Diverging lens
Forms a virtual image when the object distance is greater than the focal length.

K.C.S.E Physics Q & A - MODEL 2018PP2QN16

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP2QN16

(a) State the meaning of the following terms:
(i) Photoelectric effect
(ii) Threshold frequency
(b) Figure 5 shows some light incident on the cathode of a photocell. The photocell is connected in series with a battery, a variable resistor and a microammete

(î) Explain how the microammeter reading is affected when the intensity of the incident light is increased.
(ii) State the reason why the tube is evacuated
(c) Figure 6 shows a graph of maximum kinetic energy (KE max) of photoelectrons against the frequency of the incident radiation.

From the graph, determine:
(i) Plank’s constant h,
(ii)the threshold wavelength given that the speed of light C is 3.0 x 10⁸ms^-1

answers

(a)(i) The emission of electrons from a metal surface when light/electromagnetic radiations shine on it.
(ii) The minimum frequency of radiation required to eject electrons from a metal surface.
(b)(i) Increased intensity increases the number of electrons emitted hence a higher current reading on the microammeter.
(ii) To minimize collisions between electrons and air molecules which would cause loss of energy.

K.C.S.E Physics Q & A - MODEL 2018PP2QN15

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP2QN15

(a) Electrical energy is transmitted at very high voltages and low current
(i) Describe how the high voltages are attained
(ii) State two reasons why thick aluminum wires are preferred to Copper Wires for transmission Over long distances
(b) Figure 4 shows an electric cooker connected to the mains supply, X,Y and Z are the mains wires

State with a reason the name of wire Y.
(c) A student has some coloured bulbs rated 60 W, 240 V to be connected for decorations.
(i) State the number of such bulbs that can be connected normally to a 240V supply through a 5A fuse.
(ii) If the cost of electric energy is Ksh 3.00 per kWh, determine the cost of running the bulbs in (c) (i) for 5 hours daily for 20 days.

answers

(a)(i) By use of step-up transformers low input voltages are stepped up to high voltages for transmission.
(ii) They are cheaper
They are lighter, lower density / lower weight
b) Y is the earth wire, it is connected to the casing of the cooker

K.C.S.E Physics Q & A - MODEL 2018PP2QN14

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP2QN14

Figure 3 shows two current-carrying wires A and B passing through a cardboard.

On the diagram, sketch the magnetic field lines around the wires to show how the fields interact.

answer

State the meaning of the term battery.

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP2QN13

State the meaning of the term battery.

answer

A battery is a group of cells connected in series or parallel.

State the purpose of manganese(IV) oxide in a dry cell

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP2QN12

State the purpose of manganese(IV) oxide in a dry cell

answer

It acts as a depolarizer.

K.C.S.E Physics Q & A - MODEL 2018PP2QN11

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP2QN11

Arrange the following radiations in the order of increasing wavelengths;
Purple light, Gamma rays, infrared and ultraviolet

answer

Gamma, ultraviolet, purple light, infrared.

The sharp point of a pin is brought near the cap of a negatively charged electroscope .State and explain the observation made on the leaf of the electroscope

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP2QN10

The sharp point of a pin is brought near the cap of a negatively charged electroscope .State and explain the observation made on the leaf of the electroscope

answer

The leaf collapses
Negative charge is induced on the tip of the pin. Pin repels negatively charged air ions which discharges the electroscope.

K.C.S.E Physics Q & A - MODEL 2018PP2QN09

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP2QN09

A transformer has 600 turns in the primary coil and 9000 turns in the secondary coil. The transformer is 100% efficient and the current in the secondary coil is 0.15A, determine current in the primary coil.

answer

Define radioactivity

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP2QN08

Define radioactivity

answer

Spontaneous disintegration of atomic nuclei by emission of radiations.

K.C.S.E Physics Q & A - MODEL 2018PP2QN07

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP2QN07

Figure 2 shows the image of an object O placed on the principle axis of a convex mirror.

On the figure, draw a ray diagram to locate the object.

answer

An electric kettle is rated 1.8kW, 240 V. Determine the rating of the fuse that may be used in the kettle.

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP2QN06

An electric kettle is rated 1.8kW, 240 V. Determine the rating of the fuse that may be used in the kettle.

answer

K.C.S.E Physics Q & A - MODEL 2018PP2QN05

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP2QN05

The angle of incident for a ray of light moving from air to a certain liquid is 30. Given that the refractive index of the Liquid is 1 .36, determine the angle of refraction.

answer

State what happens to the image formed by a pin hole camera when the size of the hole is increased

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP2QN04

State what happens to the image formed by a pin hole camera when the size of the hole is increased

answer

The image is blurred.

K.C.S.E Physics Q & A - MODEL 2018PP2QN03

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP2QN03

Figure 1 shows a bar magnet AB suspended by a string.

When the North pole of another magnet is brought close to end A, there is repulsion State the polarity of end B.

answer

End B is a south pole.

State one characteristic of soft X-rays that distinguish them from hard X-rays.

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP2QN02

State one characteristic of soft X-rays that distinguish them from hard X-rays.

answer

Hard x-rays have a higher frequency than soft x-ray.
Hard x-rays have more penetrating power than soft x-rays (only one)

Explain why the walls of a studio are padded with woollen materials

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP2QN01

Explain why the walls of a studio are padded with woollen materials

answer

Sounds produced in the studio are reflected by the walls producing echoes in the room; that interfere with the signals transmitted. The woolen materials will absorb the sound hence reduce the echo effects.

K.C.S.E Physics Q & A - MODEL 2018PP1QN18

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP1QN18

(a) State two quantities that must be kept constant in order to verify Boyle’s law.
(b) An air bubble at the bottom of a beaker full of water becomes larger as it rises to the surface. State the reason why;
(i) the bubble rises to the surface,
(ii) It becomes larger as it rises.
(c) State two assumptions made in explaining the gas laws using the kinetic theory of gases.
(d) Figure 11 shows an incomplete experimental set up that was prepared by a student to verify one of the gas laws.

(i) State with a reason which one of the laws may be verified using the set up.
(ii) State what the student left out in the diagram of the set up.
(c) The volume of a fixed mass of a gas reduced from 500 cm³ to 300 cm³ at constant pressure. The initial temperature was 90K. Determine the final temperature

answers

(a) Mass
Temperature
(b)(i) The gas is less dense than the water.
(ii) As it rises the pressure around the bubble reduces and since the temperature is the same, the volume increases.
(c) The size of the molecules is assumed to be negligible.
Intermolecular forces are also assumed to be negligible.
Real gases can never have zero volume yet the gas laws assume presence of zero volume.
(d)(i) The pressure law.
Has ability to measure the temperature and the pressure while keeping the volume constant.
(ii) Source of heating for the temperature to be changed.

K.C.S.E Physics Q & A - MODEL 2018PP1QN17

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP1QN17

(a) State Pascal’s principle of transmission of pressure in liquids.
(b) Figure 10 shows heights of two immiscible liquids X and Y in a U-tube (drawn to scale).

(i) State with a reason which of the two liquids X and Y has a higher density.
(ii) Determine the value of h.
(iii) Given that the density of liquid Y is p, write down an expression for the density d of liquid X ¡n terms of p.
(c) (i) With the aid of a diagram, describe how a liquid may be siphoned from one container to another using a flexible tube.
(ii) State one application of the siphon.

answers

(a) Pressure applied at one part in a liquid is transmitted equally to all other parts of the enclosed liquid.

K.C.S.E Physics Q & A - MODEL 2018PP1QN16

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP1QN16

(a) An electric crane uses 8.0 x10⁴ N of energy to lift a load of 2.0 X 10⁴N in 4s.
(i) Determine the;
I power developed by the crane,
II height to which the load is lifted,
III efficiency of the crane whose motor is rated 2.5 X 10⁴ W.
(ii) State two forms of energy transformation that lead to the crane’s inefficiency.
(b) A stone is dropped from the top of a building to the ground. On the axes provided, sketch a graph of potential energy against time for the stone.

answers

K.C.S.E Physics Q & A - MODEL 2018PP1QN15

29/7/2020

(a) State Newton’s first law of motion.
(b) A wooden block resting on a horizontal bench is given an initial velocity u so that it slides on the bench for a distance x before it stops. Various values of x are measured for different values of the initial velocity. Figure 9 shows a graph of u² against x.

(i) Determine the slope S of the graph.
(ii) Determine the value of k given that u² = 20kd where k is a frictional constant for the surface.
(iii) State with a reason what happens to the value of k when the roughness of the bench surface is reduced.
(c) An object is thrown vertically upwards with an initial velocity of 30ms^-1. Determine its maximum height (acceleration due to gravity g is 10 ms^-1)

answers

(a) A body remains in its state of rest or uniform motion in a straight line unless acted upon by an external force.

K.C.S.E Physics Q & A - MODEL 2018PP1QN14

29/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP1QN14

(a) State two differences between boiling and evaporation.
(b) State three ways in which loss of heat by conduction is minimized in a vacuum flask.
(c) In a certain experiment, 50g of dry steam at 100 °C was directed into some crushed ice at 0 °C. (Latent heal of vaporization of water is 2.26 X 106 Jkg-1, latent heat of fusion for ice is 3.34 X 10⁵ Jkg^-1 and specific heat capacity of water is 4.2 X 10³ Jkg^-1)
Determine the;

(i) quantity of heat lost by steam to change to water at 100 °C.
(ii) quantity of heat lost by water to cool to 0°C.
(iii) mass of ice melted at 0°C.

answers

(a) Boiling takes place at fixed temperature while evaporation takes at all temperatures.
Boiling takes place in the entire liquid while evaporation takes place at the surface.
(b) - Presence of a vacuum.
- Poor conductor material used to make stopper.
- Use of glass (poor conductor).

State two ways in which a mercury based thermometer can be modified to read very small temperature changes.

28/7/2020

K.C.S.E Physics Q & A - MODEL 2018PP1QN13

State two ways in which a mercury based thermometer can be modified to read very small temperature changes.

answer

Making the bulb thinner.
Making the bore narrower

CATEGORIES

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Topics

FORM I - PHYSICS SYLLABUS

Introduction to Physics (4 Lessons)
Measurements 1 (12 Lessons)
Force (16 Lessons)
Pressure (24 Lessons)
Particulate Nature of Matter (12 Lessons)
Thermal Expansion (12 Lessons)
Heat Transfer
Rectilinear Propagation of Light and Reflection at Plane Surface (16 Lessons)
Electrostatics (12 Lessons)
Cells and Simple Circuits (12 Lessons)

FORM II - PHYSICS SYLLABUS

Magnetism (12 Lessons)
Measurements II (16 Lessons)
Turning Effect of Force (10 Lessons)
Equilibrium Centre of Gravity (12 Lessons)
Reflection at Curved Surfaces (16 Lessons)
Magnetic Effect of Electric Current (18 Lessons)
Hooke's Law (8 Lessons)
Waves (14 Lessons)
Sound (12 Lessons)
Fluid Flow (14 Lessons)

TOPICS

FORM III - PHYSICS SYLLABUS

Linear Motion (20 Lessons)
Refraction of Light (20 Lessons)
Laws of Motion (15 Lessons)
Energy, Power and Machines (20 Lessons)
Current Electricity (20 Lessons)
Waves II(10 Lessons)
Electrostatics II (15 Lessons)
Heating Effect of Electric Current (10 Lessons)
Quantity of Heat (20 Lessons)
Gas Laws (15 Lessons)

FORM IV - PHYSICS SYLLABUS

Thin Lenses (20 Lessons)
Uniform Circular Motion (10 Lessons)
Floating and Sinking (15 Lessons)
Electromagnetic Spectrum (15 Lessons)
Electromagnetic Induction (20 Lessons)
Mains Electricity (10 Lessons)
Cathode Rays and Cathode Ray Tube (10 Lessons)
X-rays (8 Lessons)
Photoelectric Effect (15 Lessons)
Radioactivity (15 Lessons)
Electronics (10 Lessons)

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