A circuit has a resistance of 12 Ω and an impedance of 15 Ω. The power factor of the circuit will be

• 0.8

• 0.4

• 1.25

• 0.125

A.

0.8

A conductor lies along the z-axis at -1.5 ≤ z< 1.5 m and carries a fixed current of 10.An in^-az direction (see figure).
B = 3.0 x 10-4 e-0.2x a_y T, find the power required to move the conductor at constant speed to x = 2.0 , y = 0  in 5 x10^-3 s. Assume parallel motion along the x axis.

• 1.57 W

• 2.97 W

• 04.85 W

• 29.7 W

A current I flows along the length of an infinitely long, straight, thin walled pipe. Then 

• the magnetic field is zero only on the axis of the pipe

• the magnetic field is different at different points inside the pipe

• the magnetic field at any point inside the pipe is zero

• the magnetic field at all points inside the pipe is the same, but not zero

A current I flows in an infinitely long wire with cross-section in the form of a semicircular ring of radius R. The magnitude of the magnetic induction along its axis is

• 
• 
  
• 
• 

D.

A red LED emits light at 0.1 watt uniformly around it. The amplitude of the electric field of the light at a distance of 1 m from the diode is:

• 1.73 V/m

• 2.45 V/m

• 5.48 V/m

• 7.75 V/m