MEDIUM
Earn 100
A metal disc is made to spin at revolutions per second about an axis passing through its centre and normal to its plane. The disc has a radius of and spins in a uniform magnetic field of , which 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 in the disc.
Important Questions on Electromagnetic Induction and Alternating Currents
MEDIUM
A very long solenoid of radius is carrying current as a function of time Counterclockwise current is taken to be positive. A circular conducting coil of radius is placed in the equitorial plane of the solenoid and concentric with the solenoid. The current induced in the outer coil is correctly depicted, as a function of time, by:
EASY
A long solenoid of diameter has turns per meter. At the centre of the solenoid, a coil of turns and radius is placed with its axis coinciding with the solenoid axis. The current in the solenoid reduces at a constant rate to from in . If the resistance of the coil is the total charge flowing through the coil during this time is
MEDIUM
A turn coil of the effective area is kept perpendicular to the magnetic field When the plane of the coil is rotated by around any of its coplanar axis in the emf induced in the coil will be:
HARD
A metallic loop is placed in a uniform magnetic field with the plane of the loop perpendicular to Under which condition (s) given an emf will be induced in the loop? "If the loop is .....
EASY
A coil of cross-sectional area having turns is placed in a uniform magnetic field . When it is rotated with an angular velocity the maximum e.m.f. induced in the coil will be:
HARD
A long solenoid of radius carries a time dependent current . A ring of radius is placed coaxially near its middle. During the time interval the induced current and the induced in the ring change as:
HARD
A conducting metal circular-wire-loop of radius is placed perpendicular to a magnetic field which varies with time as where are constants at time . If the resistance of the loop is , then the heat generated in the loop after a long time is
EASY
A small bar magnet is moved through a coil at constant speed from one end to the other. Which of the following series of observations will be seen on the galvanometer attached across the coil?
MEDIUM
A uniform magnetic field is restricted within a region of radius, The magnetic field changes with time at a rate, . Loop one of radius encloses the region, and loop two of radius, is outside the region of magnetic field as shown in the figure below. Then the emf generated is
EASY
In a coil of resistance , a current is induced by changing the magnetic flux through it as shown in the figure. The magnitude of change in flux through the coil is:
HARD
A circular insulated copper wire loop is twisted to form two loops of area and as shown in the figure. At the point of crossing the wires remain electrically insulated from each other. The entire loop lies in the plane (of the paper). A uniform magnetic field points into the plane of the paper. At , the loop starts rotating about the common diameter as axis with a constant angular velocity in the magnetic field. Which of the following options is/are correct?
MEDIUM
A conducting circular loop made of a thin wire has area and resistance It is placed perpendicular to a time-dependent magnetic field . The field is uniform in space. Then the net charge flowing through the loop during and is close to:
MEDIUM
A planar loop of wire rotates in a uniform magnetic field. Initially, at , the plane of the loop is perpendicular to the magnetic field. If it rotates with a period of about an axis in its plane then the magnitude of induced emf will be maximum and minimum, respectively at:
MEDIUM
At time magnetic field of is passing perpendicularly through the area defined by the closed loop shown in the figure. If the magnetic field reduces linearly to in the next then induced in the loop is:
MEDIUM
The relation between the charge flow through the circuit of resistance and the change in the magnetic flux is
EASY
The magnetic flux linked with a coil (in ) is given by the equation . The magnitude of induced emf in the coil at the fourth second will be:
HARD
A light disc made of aluminium (a nonmagnetic material) is kept horizontally and is free to rotate about its axis as shown in the figure. A strong magnet is held vertically at a point above the disc away from its axis. On revolving the magnet about the axis of the disc, the disc will (figure is schematic and not drawn to scale)
MEDIUM
The figure shows a bar magnet and a metallic coil. Consider four situations. (I) Moving the magnet away from the coil. (II) Moving the coil towards the magnet. (III) Rotating the coil about the vertical diameter. (IV) Rotating the coil about its axis.
An emf in the coil will be generated for the following situations.
HARD
A conducting square frame of side and a long straight wire carrying current are located in the same plane as shown in the figure. The frame moves to the right with a constant velocity . The e.m.f induced in the frame (when the centre of the frame is at a distance from the wire) will be proportional to :
MEDIUM
A metal disc of radius is rotated at a constant angular speed of in a plane at right angles to an external field of magnetic induction . The emf induced between the centre and a point on the rim will be
