A student investigates the resistance of a lamp.

1. (a)Fig. 1.1 shows the circuit used.
2. (a)(i)The student closes the switch. The readings of current I₁ and potential difference V₁ are shown in Fig. 1.2. Record the readings shown. IL = VL =[2]
3. (a)(ii)The student opens the switch. Suggest why the switch is opened after the readings are recorded.[1]
4. (a)(iii)Use the equation R=V/I to calculate the resistance R₁ of the lamp. Give your answer to 2 significant figures. RL=[2]
5. (b)(i)The student: • rearranges the circuit and connects a 10Ω resistor in series with the lamp • connects the voltmeter to measure the potential difference across the resistor and lamp combination. In the space below, draw the new circuit with the resistor added.[1]
6. (b)(ii)The reading on the voltmeter does not change. Fig. 1.3 shows the new current reading on the ammeter. This is current Ic. Record Ic. Ic = Use the equation in (a)(iii) to find the resistance Rĉ of the lamp and the resistor connected in series. Rc =[2]
7. (b)(iii)Theory states that the value of R₁ in the new circuit is given by: RL = RC-10 Calculate the resistance R₁ of the lamp. RL=[1]
8. (b)(iv)State how the brightness of the lamp changes in the new circuit compared to the circuit shown in Fig. 1.1, and explain why. change in brightness of lamp explanation[2]

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