A step down transformer connected to an ac mains supply of 220 V is made to operate at 11 V, 44 W lamp. Ignoring power losses in the transformer, what is the current in the primary circuit?

1. 2 A

2. 4 A

3. 0.2 A

4. 0.4 A

A series LCR circuit containing 5.0 H inductor, \(80~\mu F\) capacitor and 40 $\mathrm{\Omega }$ resistor is connected to 230 V variable frequency ac source. The angular frequencies of the source at which power transferred to the circuit is half the power at the resonant angular frequency are likely to be:

1. 46 rad/s and 54 rad/s

2. 42 rad/s and 58 rad/s

3. 25 rad/s and 75 rad/s

4. 50 rad/s and 25 rad/s

An inductor of inductance L, a capacitor of capacitance C and a resistor of resistance 'R' are connected in series to an ac source of potential difference 'V' volts as shown in fig. The potential difference across L, C and R is 40 V, 10 V and 40V, respectively. The amplitude of the current flowing through the LCR series circuit is \(10\sqrt{2}~A\). The impedance of the circuit will be:

1. $4 \Omega$

2.  $5 \Omega$

3. $4\sqrt{2} \Omega$

4. $5/\sqrt{2} \Omega$

A light bulb and an inductor coil are connected to an ac source through a key as shown in the figure below. The key is closed and after some time an iron rod is inserted into the interior of the inductor. The glow of the light bulb:

1.  decreases 

2.  remains unchanged 

3.  will fluctuate 

4.  increases 

An a.c. source given by V = V_m sin\(\omega t\) is connected to a pure inductor L in a circuit and I_m is the peak value of the ac current. The instantaneous power supplied to the inductor is:
1.  \(\frac{V_mI_m}{2}sin(2\omega t)\)
2.  \(-\frac{V_mI_m}{2}sin(2\omega t)\)
3.  \({V_mI_m}sin^{2}(\omega t)\)
4.  \(-{V_mI_m}sin^{2}(\omega t)\)