Alternating Current

The current that flows steadily in one direction.

• AC

• DC

• Induced current

• None of these

Current whose magnitude changes with time and direction reverses periodically

• AC

• DC

• Induced current

• All of the above

Alternating voltage (V) is represented by the equation

1. The mains ac supply in some countries is 110 V r.m.s at 50 Hz (sinusoidal).

(a) What is the peak value of voltage?

• 110 V

• 110 √ 2 V

• 110 /√ 2 V

• 550 V

Which will light a lamp more brightly, 12 V peak ac or 12 V steady dc?

• 12 V peak ac

• 12 V steady dc

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

The ? is the value of AC voltage that produces the same amount of power as a like value of DC voltage.

• peak to peak

• peak

• average

• root mean squared

Why is AC used in power distribution systems more often than DC?

• AC can be easily transformed to raise and lower voltage and current for a given amount of power.

• AC is easier to produce than DC.

• AC is safer than DC.

• AC transformers allow very high voltage levels to deliver large amounts of power at low current levels.

AC is converted from one level of voltage for transmission and then reduced to a different level of voltage for utilization by the end-user by using ? .

• Inverters

• Rectifiers

• Transformers

• Generators

With reference to the image above, what is the relationship between the voltage and current?

• They are 120 deg out-of-phase.

• They are in-phase.

• Voltage lags current.

• Current lags voltage.