A 220 V input is supplied to a transformer. The output circuit draws a current 2.0 A at 440 V. If the efficiency of the transformer is 80%, the current drawn by the primary windings of the transformer is
3.6 A
2.8 A
2.5 A
2.5 A
The two ends f a rod of length L and a uniform cross -sectional area A are kept at two temperatures T_{1} and T_{2} (T_{2} > T_{1}) .The rate of heat transfer, dQ/dt, through the rod in steady state is given by
D.
For a rod of length L and area of cross- section A whose faces are maintained at temperature T_{1} and T_{2} respectively.
Then in steady state, the rate of heat flowing from one face to the other face in time t is given by
A galvanometer having a coil resistance of 60 Ω shows full-scale deflection when a current of 1.0 A passes through it. It can be converted into an ammeter to read currents up to 5.0 A by
putting in parallel a resistance of 240 Ω
putting in series a resistance of 15 Ω
putting in series a resistance of 240 Ω
putting in series a resistance of 240 Ω
In an AC circuit, the emf (e) and the current (i) at any instant are given respectively by
e = E_{0} sin ωt
i = I_{o} sin (ωt -Φ)
The average power in the circuit over one cycle of AC is
In the circuit shown, the current through the 4 Ω resistor is 1 A when the points P and M are connected to a DC voltage source. The potential difference between the point M and N is
1.5 V
1.0 V
0.5 V
0.5 V
The primary and secondary coil of a transformer have 50 and 1500 turns respectively. If the magnetic flux Φ linked with the primary coil is given Φ = Φ_{o} +4t, where Φ is in weber, t is time is second and Φ_{o} is a constant the output voltage across the secondary coil is:
90 V
120 V
220 V
220 V
A charged particle (charge q ) is moving n a circle of radius R with uniform speed v. The associated magnetic moment μ is given by:
qvR/2
qVR^{2}
qVR^{2}/2
qVR^{2}/2
A common emitter amplifier has a voltage gain of 50, an input impedance of 100 Ω and an output impedance of 200 Ω. The power gain of the amplifier is:
500
1000
1250
1250
The core of a transformer is laminated because
energy losses due to eddy currents may be minimised
the weight of the transformer may be reduced
rusting of the core may be prevented
rusting of the core may be prevented
A coil of inductive reactance 31 Ω has a resistance of 8Ω. It is placed in series with a condenser of capacitative reactance 25Ω. The combination is connected to an a.c. soruce of 110 V. The power factor of the circuit is
0.56
0.64
0.80
0.80