4 marksAlternating Currents

CAPE Physics Unit 2 · May/June 2022 · Paper 2 · Question 2(a)

An electrical device is powered by an alternating current and is rated at 0.5 A, 50 Hz.

Derive an expression for the current waveform, in the form I = I_p sin(ωt), when the device is operating at its rated current.

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2(b)Sketch a graph of ONE cycle of the current waveform in (a), with axes labelled to show the values of the period and amplitude.[7 marks]
2(c)(i)Determine the MAXIMUM drift velocity of the charge carriers in the semiconducting cylinder if the number density of electrons is 3 × 10^17 cm^-3.[7 marks]
2(c)(ii)State how the electron drift velocity obtained in (c)(i) would compare with the electron drift velocity in a copper slug of identical dimensions carrying the…[2 marks]
2(c)(iii)The resistance of the semiconductor cylinder in (c) was measured and found to be 80 Ω. Calculate the resistivity of the semiconductor in ohmmeters.[4 marks]
2(d)Sketch and label BEFORE and AFTER diagrams to describe the formation of the depletion layer in an unbiased p-n junction.[6 marks]

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