An electron moves through a uniform magnetic field B=B0 i+2B0 j T. At a particular instant of time, the velocity of electron is u=3 i+5 j m/s. If the magnetic force acting on electron is F=5e k N, where e is the charge of electron, then the value of B0 is T.
5
F=q ( u B ) with q=e
u B=(3 i+5 j) (B0 i+2B0 j)
=6B0 k-5B0 k=B0 k
i i= j j=0, i j= k, j i=- k
5e k=eB0 k
B0=5 T
Answer: 5
A uniform magnetic field of 2 10-3 T acts along positive Y-direction. A rectangular loop of sides 20 cm and 10 cm with current of 5 A is in Y-Z plane. The current is in anticlockwise sense with reference to negative X axis. Magnitude and direction of the torque is:
Two circular coils P and Q of 100 turns each have same radius of cm. The currents in P and Q are 1 A and 2 A respectively. P and Q are placed with their planes mutually perpendicular with their centers coincide. The resultant magnetic field induction at the center of the coils is x mT, where x= . [Use 0=4 10-7 TmA-1]
Two insulated circular loops A and B of radius 'a' carrying a current of 'I' in the anti clockwise direction as shown in the figure. The magnitude of the magnetic induction at the centre will be : [figure]
The horizontal component of earth's magnetic field at a place is 3.5 10-5 T. A very long straight conductor carrying current of 2 A in the direction from South east to North West is placed. The force per unit length experienced by the conductor is 10-6 N/m.
A current of 5 A flows in a square loop of side 1 m placed in air. The magnetic field at the centre of the loop is X 2 10-7 T. The value of X is .
The deflection in moving coil galvanometer falls from 25 divisions to 5 divisions when a shunt of 24 is applied. The resistance of galvanometer coil will be :
A galvanometer having coil resistance 10 shows a full scale deflection for a current of 3 mA. For it to measure a current of 8 A, the value of the shunt should be:
Two particles X and Y having equal charges are being accelerated through the same potential difference. Thereafter they enter normally in a region of uniform magnetic field and describe circular paths of radii R1 and R2 respectively. The mass ratio of X and Y is :
A charge of 4.0 is moving with a velocity of 4.0 106 ms-1 along the positive y axis under a magnetic field B of strength (2 k) T. The force acting on the charge is x i N. The value of x is .
A proton moving with a constant velocity passes through a region of space without any change in its velocity. If E and B represent the electric and magnetic fields respectively, then the region of space may have : Choose the most appropriate answer from the options given below :