Question

Consider the situation shown in figure. The wires P1Q1 and P2Q2 are made to slide on the rails with the same speed 5 cm s−1. Find the electric current in the 19 Ω resistor if (a) both the wires move towards right and (b) if P1Q1 moves towards left but P2Q2 moves towards right.
Figure

Answer 1

Net Current is ZERO

Explanation:

(a) The wires constitute 2 parallel emf.

∴ Net emf = Blv = $1 \times 4 \times 10^-^2 \times 5 \times 10^-^2 = 20 \times 10^-^4$

Net Resistance = $\frac {2\times 2 }{2+2} + 19 = 20\ \omega$

Net Current = $\frac {20\times 10^-^4}{20} = 0.1\ mA$

(b) When both the wires move towards opposite directions then not emf = 0  

∴ Net current = 0