Question 10

Three resistors, of resistances 3 Ω, 4 Ω and 6 Ω, and a bulb are connected in a circuit,   as shown below. Initially all the switches, S1, S2 and S3, are open. The internal resistance of the battery and the resistance of the connecting wires may be ignored.

10.1 State Ohm’s law in words. (2)

Switch S1 is now closed and the voltmeter and ammeter readings are recorded. The  voltmeter and ammeter readings, when both switch S1 and switch S2 are closed, are then recorded, as well as the readings when all three switches, S1, S2 and S3, are closed.

The results obtained are shown in the table below.

10.2 Explain the increase in the ammeter reading as more switches are closed. (2)

10.3 Calculate the:

10.3.1 Resistance of the bulb (3)

10.3.2 Potential difference of the battery (4)

10.4 Define the term power. (2)

10.5 Calculate the power dissipated in the 6 Ω resistor when ONLY SWITCHES S1 and S2 are closed. (4)

10.6 How will the BRIGHTNESS of the bulb be affected as more switches in the  circuit are closed? Write only INCREASES, DECREASES or REMAINS THE SAME. (1)

10.7 Explain the answer to QUESTION 10.6. (2)

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TOTAL: 150