Physics (AS & A Level) · May / June 2016 · Paper 22 · Question 7

charge exists only in discrete amounts [1]

E = I(R + r) or V = IR (total resistance =) 2.7 + 0.30 + 0.25 (= 3.25 Ω) I = 9.0 / (2.7 + 0.30 + 0.25) or 9.0 / 3.25 = 2.8 A [3]

V = IRext = 2.77 × 3.0 or 2.8 × 3.0 or V = E – Ir (C1) = 9.0 – 2.77 × 0.25 or 9.0 – 2.8 × 0.25 V = 8.3 (8.31) V or 8.4 V [2]

I = nevA v = 2.77 / (8.5 × 1029 × 1.6 × 10–19 × 2.5 × 10–6) = 8.1 (8.147) × 10–6 m s–1 or 8.2 × 10–6 m s–1 [2]

A reduces by a factor 4 (1/4 less) or resistance of Z goes up by 4× current goes down but by less than a factor of 4 (as total resistance does not go up by a factor of 4) so drift speed goes up [2]