ALTERNATING CURRENT

The phase difference between instantaneous voltage and current of purely capacitive circuit is

• 180

• 90

• 0

• 360

The current flowing in purely capacitive circuit connected with ac source

• a. conventional current

• b. electronic current

• c. wattless current

• d. none

. For unity power factor the circuit should be

• a. purely capacitive

• b. purely resistive

• c. LCR series circuit

• d. purely inductive

An inductor of reactance 1 Ω and a resistor of 2 Ω are connected in series to the terminals of a 6 V (rms) AC source. The power dissipated in the circuit is

• a. 8 W

• b. 12 W

• c. 14.4 W

• d. 0 W

The output of a step-down transformer is measured to be 24 V when connected to a 12 W light bulb. The value of the peak current is

• a. 1/√2 A

• b. 2 A

• c. 2 √2 A

• d. 18 A

As frequency of an ac circuit increases, the current first increases and then decreases. What combination of circuit elements is most likely to comprise the circuit?

• a. Inductor and capacitor

• b. Resistor and inductor

• c. Resistor and capacitor

• d. Resistor, inductor and capacitor

Electrical energy is transmitted over large distances at high alternating voltages. Which of the following statements is (are) correct?

• a. For a given power level, there is a lower current

• b. Lower current implies less power loss

• c. Transmission lines can be made thinner

• d. It is easy to reduce the voltage at the receiving end using step-down transformers

When an AC voltage of 220 V is applied to the capacitor C

• a. the maximum voltage between plates is 220 V.

• b. the current is in phase with the applied voltage.

• d. power delivered to the capacitor is zero

• c. the charge on the plates is in phase with the applied voltage.

In an AC circuit V and I are given by V = 50 sin 50t Volt and I = 100 sin (50t + π/3) mA. The power dissipated in the circuit

• a. 2.5 kW

• b. 1.25 kW

• c. 5.0 kW

• d. 500 W

A coil of resistance 2000Ω and self-inductance 1.0 Henry has been connected to an AC source of frequency 2000/2π Hz. The phase difference between voltage and current is

• 30⁰

• 60⁰

• 75⁰

• 45⁰