Question

Consider the situation shown in figure (38-E18). The wire PQ has a negligible resistance and is made to slide on the three rails with a constant speed of 5cm/s. Find the current in the 10Ω resistor when the switch S is thrown to (a) the middle rail (b) the bottom rail.

Answer 1

B = 1T, V = 5I10^–2m/', R = 10Ω

(a) When the switch is thrown to the middle rail

E = Bvℓ

= 1 × 5 × 10^–2 × 2 × 10^–2 = 10^–3

Current in the 10  resistor = E/R

= 10^-3/10 = 10^-4 = 0.1mA

(b) The switch is thrown to the lower rail

E = Bvℓ

= 1 × 5 × 10^–2 × 2 × 10^–2 = 20 × 10^–4

current = 20 x 10^-4/10 = 2 x 10^-4 = 0.2mA