PHYSICS
PAPER 3
TIME: 2 HOURS.
Instructions to candidates
- Answer ALL the questions
- This paper consists of TWO Sections: A and B.
- ALL working MUST be clearly shown.
- Mathematical tables and electronic calculators may be used.
Question 1
You are provided with the following apparatus:
- micrometer screw gauge
- clamp
- boss
- stand
- optical pins
- Copper wire
- protractor
- Two pieces of plasticine
- cork
Procedure
- Measure the diameter of the wire using the micrometer screw gauge
d=............cm. (1mk) - Set up the apparatus as shown in the diagram below
- Bend the wire in the middle so as to make an angle of 40°. Attach the two small pieces of plasticine at both ends of the bend as shown in the diagram.
- Place the bent wire on the optical pin and give a small horizontal displacement. Note the time for 10 complete oscillations and record in the table below.
- Repeat the procedure above for other values of (8mks)
Angle θº Time t for 10 oscillations (s) Period T (s) Frequency f(Hz)= 1/T f2(Hz)2 Cos(θ/2) 40º 60º 80º 100º 120º - On the graph paper provided, plot a graph of f (y-axis) against cos θ/2 (5mks)
- Determine the gradient S of the graph(3mks)
- The equation for the oscillation of the wire is given by the formula:
f2 = 150 z cos(θ/2)
4Π2L
Given that the length of the wire L 15cm find the value of Z. (3mks)
Question 2
You are provided with the following apparatu
- A mounted wire labeled N.
- A voltmeter
- A milliammeter
- A switch
- Two dry cells and two cell holders.
- Six connecting wire with at least two crocodile clips
- Four 1000Ω resistors labelled T.
- A diode.
Procedure
- Set up the apparatus as shown below.
-
- Connect the above apparatus as shown in the circuit diagram below with the switch S open
- With the switch S open record E the voltmeter reading (1mk)
B= ______________________ - Close the switch and record V, the voltmeter reading and I, the ammeter reading (imk)
V= ______________________(1mk)
I= ______________________(1mk) - Given that: E-V=Ir. Find for the dry cell (3mks)
- Connect the above apparatus as shown in the circuit diagram below with the switch S open
-
- Now set the apparatus as shown in the set up below
- Close the switch and adjust the length x by moving the jockey along the length of the wire mounted on the metre scale till the value of x is 0cm. record the values on the Milliammeter and the voltmeter; Milliammeter.......................................A (1mk)
Voltmeter............................................A(1mk) - Repeat the experiment by now using x=10cm and note the readings on the milliammeter and voltmeter.
- Repeat ii. For other values of x and fill the table below
Distance
x(cm)0 10 20 30 40 50 60 70 80 Current I
(mA)p.d (V) - By using values obtained, plot a graph of current I against p.d. (5 mks)
- Find from the graph the value of current when p.d is 0.35V. (1 mk)
- Close the switch and adjust the length x by moving the jockey along the length of the wire mounted on the metre scale till the value of x is 0cm. record the values on the Milliammeter and the voltmeter; Milliammeter.......................................A (1mk)
MARKING SCHEME
Question 1
- Measure the diameter of the wire using the micrometer screw gauge
d=............cm. (1mk) - Set up the apparatus as shown in the diagram below
- Bend the wire in the middle so as to make an angle of 40°. Attach the two small pieces of plasticine at both ends of the bend as shown in the diagram.
- Place the bent wire on the optical pin and give a small horizontal displacement. Note the time for 10 complete oscillations and record in the table below.
- Repeat the procedure above for other values of (8mks)
Angle θº Time t for 10 oscillations (s) Period T (s) Frequency f(Hz)= 1/T f2(Hz)2 Cos(θ/2) 40º 60º 80º 100º 120º - On the graph paper provided, plot a graph of f (y-axis) against cos θ/2 (5mks)
- Determine the gradient S of the graph(3mks)
- The equation for the oscillation of the wire is given by the formula:
f2 = 150 z cos(θ/2)
4Π2L
Given that the length of the wire L 15cm find the value of Z. (3mks)
Question 2
- Set up the apparatus as shown below.
-
- Connect the above apparatus as shown in the circuit diagram below with the switch S open
- With the switch S open record E the voltmeter reading (1mk)
B= ______________________ - Close the switch and record V, the voltmeter reading and I, the ammeter reading (imk)
V= ______________________(1mk)
I= ______________________(1mk) - Given that: E-V=Ir. Find for the dry cell (3mks)
- Connect the above apparatus as shown in the circuit diagram below with the switch S open
-
- Now set the apparatus as shown in the set up below
- Close the switch and adjust the length x by moving the jockey along the length of the wire mounted on the metre scale till the value of x is 0cm. record the values on the Milliammeter and the voltmeter; Milliammeter.......................................A (1mk)
Voltmeter............................................A(1mk) - Repeat the experiment by now using x=10cm and note the readings on the milliammeter and voltmeter.
- Repeat ii. For other values of x and fill the table below
Distance
x(cm)0 10 20 30 40 50 60 70 80 Current I
(mA)p.d (V) - By using values obtained, plot a graph of current I against p.d. (5 mks)
- Find from the graph the value of current when p.d is 0.35V. (1 mk)
- Close the switch and adjust the length x by moving the jockey along the length of the wire mounted on the metre scale till the value of x is 0cm. record the values on the Milliammeter and the voltmeter; Milliammeter.......................................A (1mk)
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