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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. Suppose the 19 Ω resistor is disconnected. Find the current through P2Q2 if (a) both the wires move towards right and (b) if P1Q1 moves towards left but P2Q2 moves towards right.
Solution
(a) When the wires move in the same direction, their polarity remains the same. The circuit remains incomplete. Therefore, no current flows in the circuit.
(b) When the wires move in opposite directions, their polarities are reversed. Thus, current flows in the circuit.
\[V_{P_2 Q_2} = Blv\]
= 1 × 0.04 × 0.05
= 2 × 10−3 V
R = 2 Ω
Current in the circuit is given by
\[i = \frac{2 \times {10}^{- 3}}{2}\]
= 1 × 10−3 A = 1 mA
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