Free KCSE Physics Topical Questions KNEC Standards

K.C.S.E Physics Q & A - MODEL 2017PP2QN19

28/7/2020

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K.C.S.E Physics Q & A - MODEL 2017PP2QN19

(a) Figure 10 shows a block diagram of a cathode ray oscilloscope (CRO).

State the names of the parts labelled B₁ and B₂.
(ii) State and explain the function of the part marked A.
(b) Figure 11 shows a trace of a signal observed on the screen of a CRO. The time-base setting is 20 mscm^-2

Determine the frequency of the signal.
(c) Explain why tunsten is used as a target in an x-ray tube.

answers

a) (i) B1 — y deflecting plates
B2 — x deflecting plates
(ii) Grid; controls the intensity by controlling the number of electrons reaching the screen.
If made more negative less electrons pass through.

c) Tungsten has a high melting point.
It can with stand high temperatures.

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K.C.S.E Physics Q & A - MODEL 2017PP2QN18

28/7/2020

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K.C.S.E Physics Q & A - MODEL 2017PP2QN18

(a) State two factors that affect the capacitance of a parallel plate capacitor.
(b) Figure 9 shows an electric circuit in which three capacitors are connected across a power supply.

Determine the;
(i) total capacitance,
(ii) quantity of charge stored on the 8uF capacitor.

answers

(a) — Area of overlap of the plates
— Distance between the plates.
— Type of dielectric.

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K.C.S.E Physics Q & A - MODEL 2017PP2QN17

28/7/2020

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K.C.S.E Physics Q & A - MODEL 2017PP2QN17

(a) Figure 8 shows a conductor AB connected to a galvanometer and placed between two permanent magnets.

(i) Conductor AB is moved perpendicular to the magnetic field.
State and explain the observation made on the galvanometer.
(ii) State the effect of moving the conductor faster.
(b) A transformer is used to step down 240V to 12 V for use in an electric appliance operating at 0.5 A. If the primary coil has 600 turns, determine the;
(i) number of turns ¡n the secondary coil,
(ii) current in the primary coil.

answers

a) i. A momentary deflection is observed, Conductor cuts the field.
An emf is induced in AB Causing current in the circuit
ii. A bigger deflection is observed! higher current

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K.C.S.E Physics Q & A - MODEL 2017PP2QN16

28/7/2020

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K.C.S.E Physics Q & A - MODEL 2017PP2QN16

(a) Figure 7 shows a set up that may be used to observe photoelectric effect. A radiation is incident on the cathode. it is observed that the microammeter registers a current.

(i) Explain how the current is produced.
(ii) State with a reason what must be done for a higher current to be registered.
(iii) It was observed that for a certain incident radiation, no current was registered.
Explain this observation.
(b)A monochromatic light of wavelength 4.50 X 10^-7 m is incident on a metal surface of threshold frequency 5.5 X 10¹⁴ Hz. (Speed of light c is 3.0 X 10⁸ms and planks constant h is 6.63 X 10^-34Js).
Determine
(i) the work function of the metal surface,
(ii) average kinetic energy of the emittal photoelectrons.

answers

a)i. Radiations cause photo electrons to be ejected from the metal surface (cathode), the electrons are attracted by the anode hence current flows.
ii)Source is made moved closer! increase anode voltage/accelerating voltage.
iii. The frequency of the incident radiation is below the thrsio1d frequency of the surface hence no emission can take place.

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K.C.S.E Physics Q & A - MODEL 2017PP2QN15

28/7/2020

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K.C.S.E Physics Q & A - MODEL 2017PP2QN15

(a) Figure 5 shows the interface between glass and air.

Draw on the figure a ray diagram to illustrate the critical angle.
(b) Figure 6 shows a ray of light incident at right angles to face AB of a right angled glass prism of refractive index 1.62.

(i) Determine the critical angle of the material.
(ii) Complete the ray diagram to show the path of light until it leaves the prism.
(c)State any two applications of prisms.

answers

(c)- Dispersion of white light
- In periscopes
- In Binoculars
- In telescopes

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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)

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)

K.C.S.E Physics Q & A - MODEL 2017PP2QN19

K.C.S.E Physics Q & A - MODEL 2017PP2QN19

State the names of the parts labelled B₁ and B₂.
(ii) State and explain the function of the part marked A.
(b) Figure 11 shows a trace of a signal observed on the screen of a CRO. The time-base setting is 20 mscm^-2

K.C.S.E Physics Q & A - MODEL 2017PP2QN18

K.C.S.E Physics Q & A - MODEL 2017PP2QN18

K.C.S.E Physics Q & A - MODEL 2017PP2QN17

K.C.S.E Physics Q & A - MODEL 2017PP2QN17

K.C.S.E Physics Q & A - MODEL 2017PP2QN16

K.C.S.E Physics Q & A - MODEL 2017PP2QN16

K.C.S.E Physics Q & A - MODEL 2017PP2QN15

K.C.S.E Physics Q & A - MODEL 2017PP2QN15

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K.C.S.E Physics Q & A - MODEL 2017PP2QN19

K.C.S.E Physics Q & A - MODEL 2017PP2QN19

State the names of the parts labelled B1 and B2. (ii) State and explain the function of the part marked A. (b) Figure 11 shows a trace of a signal observed on the screen of a CRO. The time-base setting is 20 mscm-2

K.C.S.E Physics Q & A - MODEL 2017PP2QN18

K.C.S.E Physics Q & A - MODEL 2017PP2QN18

K.C.S.E Physics Q & A - MODEL 2017PP2QN17

K.C.S.E Physics Q & A - MODEL 2017PP2QN17

K.C.S.E Physics Q & A - MODEL 2017PP2QN16

K.C.S.E Physics Q & A - MODEL 2017PP2QN16

K.C.S.E Physics Q & A - MODEL 2017PP2QN15

K.C.S.E Physics Q & A - MODEL 2017PP2QN15

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FORM III - PHYSICS SYLLABUS

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State the names of the parts labelled B₁ and B₂.
(ii) State and explain the function of the part marked A.
(b) Figure 11 shows a trace of a signal observed on the screen of a CRO. The time-base setting is 20 mscm^-2