Turn ratio in a step-up transformer is 1: 2 if a
Lechlanche cell of 1.5 V is connected across the
input, then the voltage across the output will be:

1. 0.1 V     

2. 1.5 V 

3. 0.75 V 

4. zero

In an ideal parallel LC circuit, the capacitor is
charged by connecting it to a D.C. source which
is then disconnected. The current in the circuit:

1. becomes zero instantaneously 
2. grows monotonically
3. decays monotonically
4. oscillates instantaneously

A power transmission line feeds input power at 2300V to a step down transformer with its primary windings having 4000 turns, giving the output power at 230 V. If the current in the primary of the transformer is 5A, and its efficiency is 90%, the output current would be:

1. 50 A

2. 45 A

3. 25 A

4. 20 A

At a moment (t = 0), when the charge on capacitor C₁ is zero, the switch is closed. If I₀ be the current through inductor at t = 0 , for t > 0                               

1. maximum current through inductor equals I₀/2.    

2. maximum current through inductor equals $\frac{{\mathrm{C}}_1{\mathrm{I}}_0}{{\mathrm{C}}_1+{\mathrm{C}}_2}$

3. maximum charge on ${\mathrm{C}}_1=\frac{{\mathrm{C}}_1{\mathrm{I}}_0\sqrt{{\mathrm{LC}}_2}}{{\mathrm{C}}_1+{\mathrm{C}}_2}$

4. maximum charge on ${\mathrm{C}}_1={\mathrm{C}}_1{\mathrm{I}}_0\sqrt{\frac{\mathrm{L}}{{\mathrm{C}}_1+{\mathrm{C}}_2}}$

A wire of resistance R is connected in series with an inductor of reactance $\mathrm{\omega }$L. Then quality factor of RL circuit is

1.  $\frac{R}{\omega L}$

2.  $\frac{\omega L}{\mathrm{R}}$

3.  $\frac{R}{\sqrt{R^2 + {\omega }^2{L}^2}}$

4.  $\frac{\omega L}{\sqrt{R^2 + {\omega }^2{L}^2}}$

The primary and secondary coils of a transformer have 50 and 1500 turns respectively. If the magnetic flux $\varphi$ linked with the primary coils is given by \(\phi=\phi_0+4t\), where \(\phi\) is in webers, t is time in seconds, and \(\phi_0\) is a constant, the output voltage across the secondary coil is:

Which of the following combinations should be selected for better tuning of an LCR circuit used for communication?

1.  R = 25 $\Omega$, L = 2.5 H, C = 45 $\mu F$

2.  R = 15 $\Omega$, L = 3.5 H, C = 30 $\mu F$

3.  R = 25 $\Omega$, L = 1.5 H, C = 45 $\mu F$

4.  R = 20 $\Omega$, L = 1.5 H, C = 35 $\mu F$

The core of a transformer is laminated to reduce energy losses due to  

(1) Eddy currents

(2) Hysteresis

(3) Resistance in winding

(4) None of these

A power transformer is used to step up an alternating e.m.f. of 220 V to 11 kV to transmit 4.4 kW of power. If the primary coil has 1000 turns, what is the current rating of the secondary ? Assume 100% efficiency for the transformer 

(1) 4 A

(2) 0.4 A

(3) 0.04 A

(4) 0.2 A

The primary winding of a transformer has 500 turns whereas its secondary has 5000 turns. The primary is connected to an ac supply of 20 V, 50 Hz. What will be the output of the secondary transformer?