Alternating Current

The resonant frequency of a series LCR circuit is

1. f = 2π√LC
2. f = 1/(2π√LC)
3. f = √LC
4. f = 1/LC

The average power consumed in an AC circuit is maximum when the phase angle between current and voltage is

1. 90°
2. 45°
3. 0°
4. 180°

The RMS value of an alternating voltage with maximum value 311 V is

1. 110 V
2. 220 V
3. 311 V
4. 440 V

A step-up transformer increases

1. Current only
2. Voltage only
3. Voltage and frequency
4. Resistance only

A transformer works on the principle of

1. Self-induction
2. Mutual induction
3. Electrostatic induction
4. Heating effect of current

The power factor of an AC circuit is given by

1. sin φ
2. cos φ
3. tan φ
4. sec φ

At resonance in a series LCR circuit, the condition is

1. XL > XC
2. XL < XC
3. XL = XC
4. R = 0

The impedance of a series LCR circuit is given by

1. Z = R + XL + XC
2. Z = √[R² + (XL - XC)²]
3. Z = R(XL - XC)
4. Z = XL + XC

In a purely inductive AC circuit, the current

1. Leads voltage by 90°
2. Lags voltage by 90°
3. Is in phase with voltage
4. Leads voltage by 180°

The capacitive reactance of a capacitor in an AC circuit is given by

1. XC = ωC
2. XC = 1/(ωC)
3. XC = ω/C
4. XC = C/ω

The reactance offered by an inductor in an AC circuit is

1. XL = ωL
2. XL = 1/ωL
3. XL = R
4. XL = L/ω

In a purely resistive AC circuit, the phase difference between current and voltage is

1. 90°
2. 180°
3. 0°
4. 45°

The average value of a sinusoidal alternating current over one complete cycle is

1. Maximum value
2. Zero
3. RMS value
4. Half of maximum value

The RMS value of an alternating current having peak value I0 is

1. I0
2. I0/2
3. I0/√2
4. √2I0

An alternating current is represented by I = I0 sin(ωt). The value of I0 represents

1. Average current
2. RMS current
3. Peak value of current
4. Frequency of current