9. Electricity
A section of Physics, 9702
Listing 10 of 370 questions
The ends of a metal resistance wire are connected to a battery of electromotive force (e.m.f.) 8.0 V and negligible internal resistance, as shown in . 8.0 V resistance wire The power dissipated by the resistance wire is 36 W. Calculate: the current in the resistance wire current = A the number of free electrons that pass through the resistance wire in a time of 50 s number = the resistance of the wire. resistance = Ω The metal of the resistance wire in the circuit has a resistivity of 1.4 × 10–6 Ω m. The cross-sectional area of the wire is 0.25 mm2. Determine the length of the wire. length = m The circuit shown in is modified by replacing the original resistance wire with a second resistance wire. The second wire has a greater diameter than the original wire. There are no other differences between the second wire and the original wire. By reference to resistance, state and explain whether the power dissipated by the second wire is more than, less than or the same as the power dissipated by the original wire. The circuit shown in is modified by connecting a second battery, of e.m.f. 8.0 V and negligible internal resistance, in parallel with the original battery and the original resistance wire, as shown in . 8.0 V 8.0 V original resistance wire By reference to the current in the resistance wire, state and explain whether the addition of the second battery causes the power in the original resistance wire to decrease, increase or stay the same.
9702_m22_qp_22
THEORY
2022
Paper 2, Variant 2
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A circuit contains three similar lamps A, B and C. The circuit also contains three switches, S1, S2 and S3, as shown in . One of the lamps is faulty. In order to detect the fault, an ohm-meter (a meter that measures resistance) is connected between terminals X and Y. When measuring resistance, the ohm- meter causes negligible current in the circuit. shows the readings of the ohm-meter for different switch positions. Identify the faulty lamp, and the nature of the fault. faulty lamp: nature of fault: Suggest why it is advisable to test the circuit using an ohm-meter that causes negligible current rather than with a power supply. Use A C B S2 S1 S3 X Y open closed open open ∞ 15 Ω 30 Ω 15 Ω open open closed closed open open open closed switch S1 S2 S3 meter reading / Ω [T Determine the resistance of one of the non-faulty lamps, as measured using the ohm- meter. resistance = …………………… Ω Each lamp is marked 6.0 V, 0.20 A. Calculate, for one of the lamps operating at normal brightness, its resistance, resistance = …………………… Ω its power dissipation. power = …………………… W Comment on your answers to and .
9702_s06_qp_2
THEORY
2006
Paper 2, Variant 0
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Questions Discovered
370