A circular wheel of 24 spokes is rotated at 300 rpm in a uniform magnetic field of 210-3 tesla. Length of each spoke is 25 cm and the magnetic field is along the axis of the wheel, then the value of induced emf between rim and center of the wheel is
1. 1.96mV
2. 19.6V
3. 47.1mV
4. 19.6mV
When the length of a solenoid and number of turns per unit length is doubled, then the self-inductance of solenoid becomes/remains
1. 4 times
2. 2 times
3. Unchanged
4. 8 times
When the current through a solenoid increases at a constant rate, the induced current
1. is constant and is in the direction of inducing current.
2. is constant and is in the direction opposite to the inducing current.
3. is increasing and is in the direction of inducing current.
4. is increasing and is in the direction opposite to inducing current.
A non-conducting ring having a uniformly distributed negative charge is placed in the plane of smooth paper. A uniformly decreasing inward magnetic field is passing through the ring. Then,
1. Ring will start rotating anticlockwise.
2. Ring will start rotating clockwise.
3. Ring will jump and becomes floating above the paper.
4. No change will be observed in the position of the ring.
A motor having an armature resistance 2 is operating at 220 volts. At full speed, the back emf of the motor is 200 volts. Then the value of current in the armature at full speed is
1. 100 A
2. 10 A
3. 110 A
4. 0.55 A
The current I in an inductance coil varies with time t according to the graph shown in the figure. Which one of the following plots shows the variation of voltage in the coil with time?
1. | 2. | ||
3. | 4. |
A square loop enters into a uniform magnetic field. The sides of the square are 5 cm and its speed is 1 cm/s. Its front edge enters into the magnetic field at t=0, then which curve represents the variation of induced emf V?
1. 2.
3. 4.
The figure shows a current-carrying wire whose current is increasing continuously, then the direction of induced current in the conducting loop placed in the plane of paper is?
1. Anticlockwise
2. Clockwise
3. Zero
4. First clockwise then anticlockwise
Work done in increasing the current through a solenoid from 0 to 2 A is 20 J. Work done in increasing the current from 4 A to 6 A is:
1. | 100 J | 2. | 60 J |
3. | 80 J | 4. | 120 J |
A wire of length 6 m is rotated about the axis passing through point C and parallel to the magnetic field lines with angular velocity 4 radian/second. If B = 0.5T, the potential difference across the ends of the wire is
1. 2 V
2. 6 V
3. 12 V
4. Zero