Physics
A bar magnet is kept along the axis of a circular coil as shown in the figure given below. The magnet is rotated (i) about its own axis and (ii) about an axis perpendicular to the length of the magnet. The induced emf is generated at the terminals of the coil in :
- (i) only
- (ii) only
- none of the cases
- both the cases
Answer
(ii) only
Reason — Induced emf is produced only when there is a change in magnetic flux through the coil.
When the magnet is rotated about its own axis (i), the magnetic field linked with the coil does not change, so no emf is induced.
However, when it is rotated about an axis perpendicular to its length (ii), the magnetic flux through the coil changes continuously, thus inducing an emf.
Hence, the induced emf is generated at the terminals of the coil in (ii) only
Related Questions
A step up transformer …………… the current whereas a step down transformer …………… the current.
- increases, increases
- decreases, decreases
- decreases, increases
- increases, decreases
Out of the following, which statement is incorrect ?
- The lamination of core prevents loss of energy due to eddy currents.
- The core is made of soft iron.
- A transformer can be used with d.c.
- A closed core is used so as to provide a closed path for magnetic field lines.
(i) The number of turns in the secondary coil of a transformer is 20 times than that in a primary coil. If the power fed to the primary coil is 100 W (assume no energy loss), then what is the power output at the secondary coil ?
- 5 W
- 100 W
- 2000 W
- 4000 W
(ii) If the primary coil of the above transformer is supplied with 10 V, what is the voltage of the secondary coil ?
- 0.5 V
- 10 V
- 200 V
- 100 V
An electron moves on a straight line path XY as shown. abcd is a coil adjacent to the path of electron. The direction of induced current, if any, in the coil will be :
- No curent is induced
- abcd
- adcb
- No fixed direction