9.1. Electric current
A subsection of Physics, 9702, through 9. Electricity
Listing 10 of 46 questions
Define the coulomb. A resistor X is connected to a cell as shown in . ; l $ I The resistor is a wire of cross-sectional area A and length l. The current in the wire is I. Show that the average drift speed v of the charge carriers in X is given by the equation v = I nAe where e is the charge on a charge carrier and n is the number of charge carriers per unit volume in X. A 12 V battery with negligible internal resistance is connected to two resistors Y and Z, as shown in . 12 V Y Z The resistors are made from wires of the same material. The wire of Y has a diameter d and length l. The wire of Z has a diameter 2d and length 2l. Determine the ratio average drift speed of the charge carriers in Y average drift speed of the charge carriers in Z . ratio = Show that resistance of Y resistance of Z = 2. Determine the potential difference across Y. potential difference = V Determine the ratio power dissipated in Y power dissipated in Z . ratio =
9702_s16_qp_21
THEORY
2016
Paper 2, Variant 1
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The current in a wire is I. Charge Q passes one point in the wire in time t. State the relation between I, Q and t, which of the quantities I, Q and t are base quantities. The current in the wire is due to electrons, each with charge q, that move with speed v along the wire. There are n of these electrons per unit volume. For a wire having a cross-sectional area S, the current I is given by the equation I = nSqv k, where k is a constant. State the units of I, n, S, q and v in terms of the base units. I n S q v By considering the homogeneity of the equation, determine the value of k. k = …………………………
9702_w08_qp_2
THEORY
2008
Paper 2, Variant 0
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Questions Discovered
46