In the configuration shown in the figure, the wire PQ has negligible resistance and slides across the three rails at a constant speed of 5 cm s ⁻¹ . Calculate the current in the 10 resistor when the switch S is thrown to the bottom rail.

Step-by-step solution

When the switch S is thrown to the bottom rail, the active circuit loop is formed by the top rail, the bottom rail, the wire PQ , and the 10 resistor. The effective length of the wire PQ that moves in the magnetic field and forms part of the circuit is the distance between the top and bottom rails: l = 2 cm + 2 cm = 4 cm = 0.04 m The motional electromotive force (EMF) induced in the wire is given by: = Bvl Substituting the given values ( B = 1.0 T , v = 5 cm s ⁻¹ = 0.05 m s ⁻¹ , l = 0.04 m ): = 1.0 0.05 0.04 = 0.00