Name…………………………………………………………….	Index No……………………………..

School……………………………………………………………	Candidate’s sign…………………….

Date………………………………….

232/1

PHYSICS

Paper 1

July/August 2016

2 hours

BUSIA SUB-COUNTY JOINT EXAMINATIONS – 2016

Kenya Certificate of Secondary Education (K.C.S.E)

232/1

PHYSICS

Paper 1

July/August 2016

2 hours

Instructions to candidates.

1.	Write your name and index number in the spaces provided above

2.	Sign and write the date of examination in the spaces provided above

3.	This paper consists of two sections: A and B

4.	Answer all the questions in section A and B in the spaces provided

5.	all working must be clearly shown

3.	Mathematical tables and silent electronic calculators may be used.

FOR EXAMINER’S USE ONLY.

SECTION	MAXIMUM SCORE	CANDIDATES SCORE
A	1 – 12	25
B	13	09
14	10
15	12
16	15
17	09
TOTAL SCORE	80

This paper consists of 16 printed pages. Candidates should check the question paper to

Ensure that all the pages are printed as indicated and no questions are missing.

SECTION A (25MKS)

The diagram in the fig. shown an object o placed in front of a converging lens. F1 and F2 are the principal foci for the lens.

F1	F2

Using correct rays, locate the imaged formed.	( 2mks)

Two similar bulb, are connected in series (a) and in parallel ( b)

If bulb 1 is unscrewed in both cases what happens to bulb 2	( 1mk)

Water from a tap near a positively charged rod as shown.

Explain why the water is attracted towards the rod	(2mks)

a) State a reason why the magnetic field strength of a magnet are strong at the poles.	( 1mk)

b). The diagram below shows a method of magnetization

Ferromagnetic material is being magnetized

State the polarity of end B	(1 mk)

The fig. below shows a standing wave formed when a string of length 1.5m stretched between two supports and plucked at the centre.

Determine the wave velocity if 4 waves were produced every second	( 3mks)

The lighting circuit in a house has 18 lamps each with a rating of 60w, 240v. Given 5A and 13A fuses, determine the rating of a fuse that can be used safely in the circuit when all the lamps are put on	( 2mks)

Name two types of electromagnetic radiations whose frequencies are greater than that of visible light	( 1mk)

A thermister TH is connected in parallel while a bulb as shown in fig. below, the bulb is lit. When the thermister is steadily heated, the brightness of the bulb reduces. Explain the observation. ( 2mks)

The fig below shows a battery of 6.0V connected in parallel with two capacitors.

Determine the charge stored in the combined capacitor when the switch is closed	(3mks)

The force on a conductor carrying current in a magnetic field can be varied by changing among other factors the magnitude of the current. Name two other factors that can be changed to the force. (2mks)

a) The fig. below shows a ray of light incident on a convex mirror

Using a suitable construction, on the same diagram, determine the radius of curvature of the mirror.	( 2mks)

The human ear can distinguish two sounds as separate only if they reach at at 0.1 sec apart. How far from a wall must an observer be in order to hear an echo when he shouts ( speed of sound in air is 330mls).	( 2mks)

The diagram below shows a bar magnet being withdrawn from a solenoid.

The centre zero galvanometer is observed to deflect in the direction shown. What is the polarity of the magnet at B.	(1mk)

SECTION B ( 55 MARKS)

a) State ohm’s law	( 1mk)

b). Two resisters, one of 4Ç resistance and the other of unknown resistance x are connected in a

circuit as shown in fig below.

The current (i) passing through the combination is measured for various potential difference (p.d). A graph p.d against current is shown below.

Use the graph to determine the:

Total resistance of the combination	( 3mks)

Value of the unknown resistance X	( 2mks)

c). The following appliance are operated in a home for the indicated every day.

Appliance	Time

Three 40W bulbs	3 Hrs

One 2000W Television	5 Hrs

Four 60W bulb	30 mins

One 500W freezer	10Hrs

Calculate

The total power used by the appliance everyday	( 2mks)

The total electrical power consumed 30 days in kwh	( 2mks)

If the cost per unit is Kshs. 7.50cts. calculate the cost of using the appliance in 30 days	( 2mks)

A ray of monochromatic light passed through the glass prism as shown in fig. Below.

State the name given to what happens at A and B	( 2mks)

A

B

Use the angles on the diagram to calculate the angle of refraction at A.	( 2mks)

Calculate the refraction index of glass	( 2mks)

b. In an experiment on interference, light of wavelength was place near two narrow slits x and y.

Describe what is observed on the screen	( 2mks)

State what is observed on the screen when:

The slit separation xy is reduced	(1mk)

White light is used instead of monochromatic light	(1mk)

The fig. shown a chematic diagram of a diffusion cloud chamber used for detecting radiations from a radio active source.

ai). State with reason why alcohol is preferred over the other substances for use in this experiment.	( 1mk)

ii). Briefly explain how radiaton’s from the radioactive source are detected in the chamber.	( 3mks)

iii). In an experiment to determine the half – life of a radioactive substance using a G – M tube, the

activity of the sample was represented on the graph shown below.

Form the graph determine:

The background radiation given that at t = 0, the counter rate was 900 counter rate / min	( 1mk)

The half life	( 1mk)

The fig below shown radiation introduced in a magnetic field.

Identify radiations U and W	( 2mks)

U

W

Explain the difference in the shapes of U and W	( 1mk)

What is the half – life of radioactive substance is its activity falls 1/8 of its initial valve in 3360 seconds?	( 2mks)

How can the wave length of x – rays produced in this tube be reduced	( 1mk)

X – ray are emitted when a tube operates at 3.0 x 102V and a current of 0.0lA is passing through it.

Take e=1.6 x10-19C,	Me = 9.0 x10-31kg,	h= 6.63x 10-34 Js .

Calculate

ii. The velocity of the electron on hitting the target	( 3mks)

iii. The minimum wavelength of x – rays emitted assuming that all electrons energy converted to x – rays	( 2mks)

The graph below was obtained on a C.R.O screen when output of a a.c generator was connected. The time base control was set at 20ms/cm air and its y – gain at 5V/cm.

Determine

The peak voltage of the generator	( 2mks)

The frequency of the input signal	(3mks)

b). The work function of a certain surface is 3.2 e.V. Determine the thresh hold frequency for the surface.

( h= 6.62 x 10-34js)	( 3mks)

a). define the term doping	( 1mk)

b). The fig. shows a depletion layer in unblessed p –n junction

By drawing, connect the p-n junction with a battery so as to be used to make the depletion layer narrower.	( 1mk)

The fig. shows an incomplete circuit of a full wave rectification.

Draw in the figure two more diodes, D3 and D4 to complete the circuit	(1mk)

c). Describe how the illustrated rectifier works	(3mks)

d i). A capacitor may be connected across the load resistor r in the fig. above. State the role of the capacitor	( 1mk)

Sketch on the axis below how the out put signals is displaced on a C.R.O screen after a capacitor has been connected	(1mk)

Volts

Time