### KCSE CLUSTER TESTS 27

#### Physics Paper 3

1.

You are provided with the following

- A converging lens on a lens holder.

- A screen fitted with cross-wires labeled O

- A mounted white screen labeled S

- A meter rule - Two dry cells

- A mounted torch bulb

- Connecting wires and switch

- A retort stand boss and clamp

Proceed as follows;
a) Find an approximate value of the focal length f of the converging lens supplied.

Æ’=________________________________________mm

Explain briefly how the value of f was obtained

b) Arrange the apparatus as shown below

_____________________________________________________________________

20 marks

2.

You are provided with the following;

- A retort stand, boss and clamp.

- Test tube

- Piece of duplicating paper

- A thermometer

- A large beaker containing some water

- A tripod stand and wire gauze

- A cardboard with a hole in the middle

- A burner

- A rubber band

- A stop band

- A stop watch
Proceed as follows;
a) Set up the apparatus as shown below.

b) Heat the water in the beaker provided and leave it to boi

l c) Wrap the given piece of duplicating paper round the bulb of the thermometer. Use rubber band to hold the paper in place.

d) Place the thermometer inside in the dry test tube.

e) Place the test tube in the water as shown in the diagram above. Make sure that the water does not enter the test tube. Leave the test tube in the boiling water until the thermometer indicates a steady temperature.

f) Remove the thermometer and immediately start the stop watch.

g) While holding the thermometer in air record the readings of the thermometer T1 at intervals of 30seconds for 10 minutes

h) Place the wrapped thermometer directly into boiling water. Leave the thermometer in the boiling water until it indicates a steady temperature.

i) Repeat procedure (f) and (g) and record the reading T2 of the thermometer in the table at half minute intervals for 5minutes. j) Using the same axes on the grid provided, plot a graph of temperature (y-axis) against time for result obtained in (g) and (i) (label the graph T1 and T2)
Graph
k) From the graphs determine; i. For each graph the time for temperature to fall from 600C

ii. Find the ratio of the two times in k (i) above

20 marks

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