A long vertical wire carries a steady 40 A current. A pair of rails are horizontal and ...

Figure 21.3

A long vertical wire carries a steady 40 A current. A pair of rails are horizontal and are apart. A 20 ohm resistor connects points a and b, at the end of the rails. A bar is in contact with the rails, and is moved by an external force with a constant velocity of as shown. The bar and the rails have negligible resistance. At a given instant t₁, the bar is from the wire, as shown. In Figure 21.3, at time t1, the induced current and its direction through the resistor are closest to:

• 0.12 μA, from a to b

• 0.060 μA, from a to b

• 0.36 μA, from b to a

• 0.060 μA, from b to a

• 0.12 μA, from b to a