## PHYSICS PAPER 3 - 2019 LANJET JOINT MOCK EXAMINATION

QUESTION 1

You are provided with the following apparatus:

• Ammeter
• Voltmeter
• Mounted resistance wire labeled W
• A new dry cell
• A cell holder
• 8 connecting wires
• A switch
• A jockey
• Micrometer screw gauge (to be shared)

PART A
PROCEED AS FOLLOWS:

1. Connect your apparatus as shown in the figure 2. Place the jockey at L=10cm, close the switch S. Read and record the current and the P.d readings.
Current (I) =……………A                                                             (1/2mk)
P.d (V) =………………….V                                                             (1/2mk)
3. Repeat the procedure in (b) for other values of L, and complete the table below. (5mks)
 length L(cm) 10 15 20 25 30 35 P.d.(V) Current I(A)
4. Plot a graph of p.d (V) against current (I) in the graph paper provided. (5mks) 5. Determine the slope S of the graph (3mks)
6. Given that the relationship between p.d (V) and current (I) supplied from the cell is given by the equation E=V+Ir, use your graph to determine the values of
E=………………… (1mk)
r=………………… (1mk)

PART B

Re-arrange the apparatus as show below 1. Close the switch S and record the current, (I) and the P.d (V) readings.
I=………………………A
V=………………………V                                        (1mk)
2. Use your values in (f) above to calculate the resistance R, of the wire, W.
R=………………Ω                                                                (1mk)
3. Measure the diameter d of the wire, W, using a micrometer screw gauge. Give your answer in SI units.
d=………………….                                                              (1mk)
4. Given that R= 4Ɓ/(πd^2 ), find the value of Ω for the wire W.              (1mk)

QUESTION 2

You are provided with the following apparatus:

• A 250cm3 glass beaker
• A candle
• A metre rule
• White screen
• Water

PROCEED AS FOLLOWS:

1. Set up the apparatus as shown in the figure below. 2. Put about 200cm3of water into the beaker. Measure the height, h of the water above the base of the beaker.
3. Given the internal radius, r of the beaker is given by the relation r=√(100/h) . Find the value of r.
r =……………cm              (2mks)
4. Adjust the position of the screen until a sharp image is formed on the screen.
Read and record the corresponding values of U and V In the table below. Given that U = 10r, 9r, 8r… (8mks)
 10r 9r 8r 7r 6r 5r 4r 3r U (cm) V(cm)
5. Plot a graph of u against v. (5mks) 6. Determine the slope at 6r. (3mks) ## MARKING SCHEME

PART A

 L(CM) 10 15 20 25 30 35 P.d (V) 1 1.1 1.15 1.2 1.25 1.3 I(A) 0.4 0.32 0.28 0.24 0.2 0.16  QUESTION 2
H=3.0 cm
r=5.77cm

 10r 9r 8r 7r 6r 5r 4r 3r U(cm) 17.3 22.8 28.7 33.8 39.3 44.8 50.3 54.1 V(cm) 16.9 13.7 11.9 11.7 10.7 10.2 10.1 10.0 Slope = change in y /change in x

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