# A conducting rod PQ of length L = 1.0m is moving with a uniform speed v = 20 ms-1 in a uniform magnetic field….

Q. A conducting rod PQ of length L =  1.0 m is moving with a uniform speed v = 20 ms-1 in a uniform magnetic field B = 4.0 T directed into the plane of the paper. A capacitor of capacity C = 10 μF is connected as shown in figure, then

(a)qA = +80 mC and qB = -80 mC

(b)qA = -80 mC and qB = +80 mC

(c)qA = 0 = qB

(d)charge stored in the capacitor increases exponentially with time

Ans: (a)

Sol: EMF induced in the rod , $\displaystyle E = B L v$

$\displaystyle E = 4 \times 1 \times 20$

E = 80 volt

Since q = CE = 10 × 10-6 × 80

q = 8 × 10-4 C

q = 80 mC

Since , rod is moving towards right & field is(x)

A is +vely charged & B is -vely charged .