Motional Electromotive Force (e.m.f.)

Find the current in the sliding rod AB (resistance = R) for the arrangement shown in figure. B is constant and is out of the paper. Parallel wires have no resistance. v is constant. Switch S is closed at time t = 0.

A metal disc of radius 30 cm spins at 20 revolution per second about its transverse symmetry axis in a uniform magnetic field of 0.20 T. The field is parallel to the axis of rotation. Calculate
(a) the area swept out per second by the radius of the disc
(b) the flux cut per second by a radius of the disc
(c) the induced emf between the axle and rim of the disc.

A wire of length 50 cm moves with a velocity of 300 m/min, perpendicular to a magnetic field. If the e.m.f. induced in the wire is 2 V, the magnitude of the field in tesla is ______.

A circular coil expands radially in a region of magnetic field and no electromotive force is produced in the coil. This can be because ______.

1. the magnetic field is constant.
2. the magnetic field is in the same plane as the circular coil and it may or may not vary.
3. the magnetic field has a perpendicular (to the plane of the coil) component whose magnitude is decreasing suitably.
4. there is a constant magnetic field in the perpendicular (to the plane of the coil) direction.

An e.m.f is produced in a coil, which is not connected to an external voltage source. This can be due to ______.

1. the coil being in a time varying magnetic field.
2. the coil moving in a time varying magnetic field.
3. the coil moving in a constant magnetic field.
4. the coil is stationary in external spatially varying magnetic field, which does not change with time.

Find the current in the wire for the configuration shown in figure. Wire PQ has negligible resistance. B, the magnetic field is coming out of the paper. θ is a fixed angle made by PQ travelling smoothly over two conducting parallel wires separated by a distance d.

A rectangular loop of wire ABCD is kept close to an infinitely long wire carrying a current I(t) = Io (1 – t/T) for 0 ≤ t ≤ T and I(0) = 0 for t > T (Figure). Find the total charge passing through a given point in the loop, in time T. The resistance of the loop is R.

Consider the situation shown in the figure. Suppose the wire connecting O and C has zero resistance but the circular loop has a resistance Runiformly distributed along its length. The rod OA is made to rotate with a uniform angular speed ω as shown in the figure. Find the current in the rod when ∠ AOC = 90°.