A coil of resistance 400 is placed in magnetic field. If the magnetic flux Φ (Wb) linked with the coil varies with time t (sec) as Φ = 50t2 +4.
The current in the coil at t= 2 s is
0.5 A
0.1 A
2 A
2 A
Two similar coils of radius R are lying concentrically with their planes at right angles to each other. The currents flowing in them are I and 2I, respectively. The resultant magnetic field induction at the centre will be
The potential energy of a particle in a force field is, where A and B are positive constants are r is the distance of a particle from the centre of the field. For stable equilibrium, the distance of a particle is
B/2A
2A/B
A/B
A/B
In an electrical circuit R, L, C and AC voltage source are all connected in series when L is removed from the circuit, the phase difference between the voltage and the current in the circuit is π/3. If instead, Cis removed from the circuit, the phase difference is again π/3. The power factor of the circuit is
1/2
1
1
A millivoltmeter of 25 mV range is to be converted into an ammeter of 25 A range. The value (in ohm) of necessary shunt will be
0.001
0.01
1
1
A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole. it
will become rigid showing no movement
will stay in any position
will stay in the north-south direction only
will stay in the north-south direction only
The electric field associated with an electromagnetic wave in vacuum is given by E=i 40 cos (kz-6x108t), where E, z= and t are in volt/m, metre and second respectively. The value of wave vector k is
2 m-1
0.5 m-1
6 m-1
6 m-1
What is the flux through a cube of side a if a point charge of q is a one of its corner?
A ring is made of wire having a resistance Ro = 12Ω. Find the points A and B, as shown in the figure, at which a current carrying conductor should be connected so that the resistance R of the subcircuit between these points is equal to 8/3Ω
D.
If voltage across a bulb rated 220 V -100W drops by 2.5% of its rated value, the percentage of the rated value by which the power would decrease is
20%
2.5%
5%
5%