A small circular wire loop of radius a and number of turns N, is oriented with its axis parallel to the direction of the local magnetic field B. A resistance R and a galvanometer are connected to the coil, as shown in the figure.
When the coil is flipped (i.e., the direction of its axis is reversed) the galvanometer measures the total charge Q that flows through it. If the induced emf through the coil EF = IR, then Q is
1
πNa2В/(2R)
2
πNa2В/R
3
√2πNa2В/R
4
2πNa2В/R