A transformer having efficiency of 90% is working on 200 V and 3 kW power supply. If the current in the secondary coil is 6 A, the voltage across the secondary coil and the current in the primary coil respectively are: 

• 300 V, 15 A

• 450 V, 15 A

• 450 V, 13.5 A

• 450 V, 13.5 A

In an AC circuit, an alternating voltage 100t volt is connected to a capacitor of capacity 1μF. The rms value of the current in the circuit is 

• 100 mA

• 200 mA

• 20 mA

• 20 mA

An AC voltage is applied to a resistance R and an inductor L in series. If R and the inductive reactance are both equal to 3Ω, the phase difference between the applied voltage and the current in the circuit is 

• π/4

• π/2

• zero

• zero

In the given figure, a diode D is connected to an external resistance R = 100 Ω and an e. m. f of 3.5 V. If the barrier potential developed across the diode is 0.5 V, the current in the circuit will be 

• 30 mA

• 40 mA

• 20 mA

• 20 mA

105.

The rms value of potential difference V shown in the figure is 

• V_o

• 

• V_o/2

• V_o/2

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 T₁ and T₂ (T₂ > T₁) .The rate of heat transfer, dQ/dt, through the rod in steady state 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 = E₀ 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