10. D.C. circuits
A section of Physics, 9702
Listing 10 of 271 questions
State Kirchhoff’s first law. A battery of electromotive force (e.m.f.) 12.0 V and internal resistance r is connected to a filament lamp and a resistor, as shown in . r 3.6 A 2.1 A 12.0 V The current in the battery is 3.6 A and the current in the resistor is 2.1 A. The I-V characteristic for the lamp is shown in . I / A V / V 0.5 1.0 1.5 2.0 2.0 4.0 6.0 Determine the resistance of the lamp in . resistance = Ω Determine the internal resistance r of the battery. r = Ω The initial energy stored in the battery is 470 kJ. Assume that the e.m.f. and the current in the battery do not change with time. Calculate the time taken for the energy stored in the battery to become 240 kJ. time = s The filament wire of the lamp is connected in series with the adjacent copper connecting wire of the circuit, as illustrated in . filament wire copper wire (not to scale) Some data for the filament wire and the adjacent copper connecting wire are given in Table 6.1. Table 6.1 filament wire copper wire cross-sectional area A 360 A number density of free electrons n 2.5 n Calculate the ratio average drift speed of free electrons in filament wire average drift speed of free electrons in copper wire . ratio =
9702_m21_qp_22
THEORY
2021
Paper 2, Variant 2
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Define the volt. shows a network of three resistors. 300 Ω 100 Ω 55 Ω Y X Calculate: the combined resistance of the two resistors connected in parallel combined resistance = Ω the total resistance between terminals X and Y. total resistance = Ω The network in is connected to a power supply so that there is a potential difference between terminals X and Y. The power dissipated in the resistor of resistance 55 Ω is 0.20 W. Calculate the current in the resistor of resistance: 1. 55 Ω current = A 2. 300 Ω. current = A Calculate the potential difference between X and Y. potential difference = V
9702_s20_qp_23
THEORY
2020
Paper 2, Variant 3
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State Kirchhoff’s second law. Three identical cells, each of electromotive force (e.m.f.) 1.5 V and internal resistance 590 mΩ, are connected in parallel across a conductor, as shown in . 1.5 V 590 mΩ 1.5 V 590 mΩ 1.5 V 590 mΩ A B conductor The conductor is composed of two cylindrical sections A and B. The total resistance of the circuit is 2.2 Ω. Show that the resistance of the conductor is 2.0 Ω. Calculate the current in the conductor. current = A The two cylindrical sections A and B of the conductor in are made from the same material and have the same length. The diameter of section A is 4.3 mm and the diameter of section B is 7.6 mm. The resistance of section A is RA and the resistance of section B is RB. Calculate the ratio RA RB . RA RB = Calculate the ratio average drift speed of free electrons in section A average drift speed of free electrons in section B . Explain your reasoning. ratio = The circuit of is altered by removing one of the cells. State and explain the effect, if any, of this change on the potential difference across the conductor.
9702_w22_qp_23
THEORY
2022
Paper 2, Variant 3
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Questions Discovered
271