Assessment for learning. AC

Assessment for learning. AC

LO

• describe the processes occurring in AC circuits containing resistance;

• Apply the Ohm’s law for complete AC circuit containing reactance;

• Use Ohm’s law for complete AC circuit; 

• deduce that the mean power in a resistive load is half the maximum power for a sinusoidal alternating current; 

• apply the expressions I=0.7 I0
   and U=0.7 U0 to distinguish between effective, root-mean-square and peak values of voltage and current intensity

Multiple Choice

When an AC is applied across a pure resistance:

• the voltage and current are out of phase with each other.

• the voltage and current are in phase with each other.

• the voltage leads current by 90 degree.

• the voltage lags current by 90 degree

Multiple Choice

An increase in which factors will cause an increase in the inductive reactance of circuit?

• Resistance and capacitive reactance.

• Inductance and frequency

• Resistance and voltage

Multiple Choice

In an AC circuit, the effective voltage is

• greater than the maximum instantaneous voltage.

• less than the maximum instantaneous voltage.

• equal to the maximum instantaneous voltage.

Multiple Choice

The term that describes the combined resistive forces in an ac circuit is

• resistance.

• reactance.

• impedance.

Multiple Choice

when an alternating voltage is applied across a pure inductance:

• the voltage and the current are in phase with each other.

• the voltage lags current by 90 degree.

• the voltage leads current by 90 degree.

• none of above.

Multiple Choice

when an A.V of frequency f hertz is applied acrossed a pure inductanceof L henry, X_L is:

• X_L = 2πfL

• x_{L =} 1/(2πfL)

• X_{L =} R

• X_{L =} 1/(2πfc)