Alternating Current

In an electromagnetic wave in free space the root mean square value of the electric field is E rms= 6 V/m. The peak value of the magnetic field is

• 1.41 × 10–⁸ T

• 2.83 × 10^–8 T

• 0.70 × 10^–8 T

• 0.70 × 10^–8 T

An inductor 20 mH, a capacitor 100 µF and a resistor 50 Ω are connected in series across a source of emf, V = 10 sin 314 t. The power loss in the circuit is

• 0.79 W

• 0.43

• 1.13

• 2.74 W

An AC supply gives 30V_rms which is fed on a pure resistance of 10 ohm. the power dissipated in this is

• 90watt

• 45watt

• 90.2watt

• 180watt

A transmitting station transmits radiowaves of wavelength 360 m. Calculate the inductance of coil required with a condenser of capacity 1.20 μF in the resonant circuit to receive them

• 3.07×10^-8 H

• 2.07×10^-8 H

• 4.07×10^-8 H

• 6.07×10^-8 H

The peak value of alternating current is $5\sqrt{2}$ ampere. The mean square value of current will be

• 5 A

• 2.5 A

• $5\sqrt{2}$ A

• None of the above

A lamp in which 10 amp current can flow at 15 V, is connected with an alternating source of potential 220 V. The frequency of source is 50 Hz. The impedance of choke coil required to light the bulb is

• 0.07 H

• 0.14 H

• 0.28 H

• 1.07 H

An L.C. circuit is in the state of resonance. If C = 0.1F and L = 0.25 Henry. Neglecting ohmic resistance of circuit. What is the frequency of oscillations?

• 1007 Hz

• 100 Hz

• 100 Hz

• 500 Hz

When temperature of an ideal gas is increased from 27°C to 227°C, its rms speed is changed from 400 m/s to v_s Then, v_s is

• 516 m/s

• 450 m/s

• 310 m/s

• 746 m/s

In a L-C-R circuit, the capacitance is made one-fourth, then what should be changed in inductance, so that the circuit remains in resonance?

• 8 IMES

• 1/4 times

• 2 times

• 4 times

In a circuit, L, C and R are connected in series with an alternating voltage source of frequency f. The current leads the voltage by 45°. The value of C is

• $\frac{1}{2\mathrm{\pi f} \left(2\mathrm{\pi f} \mathrm{L} + \mathrm{R}\right)}$

• $\frac{1}{\mathrm{\pi f} \left(2\mathrm{\pi f} \mathrm{L} + \mathrm{R}\right)}$

• $\frac{1}{2\mathrm{\pi f} \left(2\mathrm{\pi f} \mathrm{L} - \mathrm{R}\right)}$

• $\frac{1}{\mathrm{\pi f} \left(2\mathrm{\pi f} \mathrm{L} - \mathrm{R}\right)}$