(a) Define electromotive force.
(b) Define potential difference.
(c) A potential difference of 12 V is causing electrons to flow through a wire so that 2.0 * 1020 electrons pass a point in the wire in 1.0 minute. Calculate
(i) the charge which passes the point in 1.0 minute, given that the charge of each electron is 1.6 * 10-19 C,
(ii) the electric current in the wire an
(iii) the resistance of the wire.
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Answer:
(a) Electromotive force of an electrical energy source is defined as the work done by the source in driving a unit charge around a complete circuit.
(b) Potential difference is the amount of energy of electrical energy converted to other forms of energy when 1 C of positive charge passes between 2 points.
(c)
(i) 1 electron --> 1.6 * 10-19 C
2.0 * 1020 electrons --> 1.6 * 10-19 * 2.0 * 1020
= 3.2 * 10
= 32 C
(ii) I = Q/T
= 32/60
= 0.533 A (3 s.f.)
(iii) R = V / I
= 12 / 0.533
= 22.5 Ω
