Consider the situation shown in . The wires `P_1Q_1` and `P_2 Q_2` are made to slide on the rails with the same speed `5cm s^(-1)`. Find the electric current in the 19`Omega` resistorif (a) both the wires move towards right and (b) if `P_1 Q_1` moves towards left but `P_2 Q_2` moves towards right.

Options

A. zero
B. `0.2 mA
C. 0.3 mA
D. None of these

Answer

A

Explanation

The wire constitue two parallel emf, Net emf = Blv
`1 xx 4 xx10^(-2) xx 5 xx 10^(-2) xx 5 xx 10^(2)=20 xx 10^(-4)`
Net resistance `= (2+2)/(2+2)+19 = 20 Omega`
Net current `= (20 xx 10^(-4))/(20)=0.1 mA` .
When both wires move toward opposite directions then net emf`=0`
`:.` Net current `=0`.