AC Current

The period of a wave is

• the same as frequency
• time required to complete one cycle
• expressed in amperes
• none of the above

A heater is rated as 230 V, 10 kW. The value 230 V refers to

• average voltage
• r.m.s voltage
• peak voltage

In a series resonant circuit,the impedance of the circuit is

• minimum
• maximum
• zero

The r.m.s value of an alternating current is given by steady (D.C) current which when flowing through a given circuit for a given time produces

• the more heat than produced by A.C when flowing through the sam circuit
• the less heat than produced by A.C when flowing through the sam circuit
• the same heat than produced by A.C when flowing through the sam circuit

In a pure inductive circuit

• the current is in phase with voltage
• the current lags behind the voltage by 90 degrees
• the current leads the voltage by 90 degrees
• the current can lead or lag voltage by 90 degrees

In an RLC circuit, power loss can take place in

• R
• L
• C
• L and C

Poor power factor

• reduces load handling capability of electrical system
• results in more power losses in electrical system
• results in less power losses in electrical system
• overloads the power supply

If a sinusoidal wave has a frequency of 50 Hz with 30 A r.m.s current, which of the following equation represents the wave?

• 42.42 sin 314.2t
• 60 sin 25t
• 30 sin 50t
• 84.84 sin 25t

In a pure inductive circuit, if the supply frequency is reduced to 1/2, the current will 

• be reduced by half
• be doubled
• be four times as high
• be reduced to one fourth

Capacitive reactance is more when

• capacitance is less and frequency of supply is less
• capacitance is less and frequency of supply is more
• capacitance is more and frequency of supply is less
• capacitance is more and frequency of supply is more