Resistance & Inductance in AC Circuits

What law governs the current that flows through a pure resistance connected across an alternating current supply?

• Ohm's Law

• Lenz's Law

• Faraday's Law

• Kirchhoff's Current Law

In a purely resistive circuit, how is the current through the resistor affected by the frequency of the supply?

• It increases with frequency

• It is unaffected by the frequency

• It is inversely proportional to the frequency

• It decreases with frequency

What is the unit of self-inductance?

• Tesla

• Farad

• Henry

• Ohm

What happens to the inductive reactance if the frequency of the supply is increased?

• It increases

• It becomes zero

• It decreases

• It remains constant

What is the formula to calculate the power consumed by a resistor connected across an a.c. supply?

• P = I^2.R

• P = V/I

• P = V^2/R

• P = V.I.cos φ

How does the current in an inductive circuit compare to the voltage across the coil?

• The current and voltage are in phase

• The current lags the voltage by 90°

• The current and voltage are completely out of sync

• The current leads the voltage by 90°

What is the effect of inductance on the steady flow of a direct current through a coil?

• It decreases the current

• It reverses the current

• It increases the current

• It has no effect

How is the supply voltage calculated in a circuit with resistance and inductance in series?

• Using Pythagoras theorem

• By multiplying the voltages across the resistor and inductor

• By subtracting the voltage across the inductor from the resistor

• By adding the voltages across the resistor and inductor

What does the power factor of a circuit indicate?

• The efficiency of the circuit

• The resistance of the circuit

• The phase difference between voltage and current

• The total power consumed by the circuit

If the voltage across a resistor (V_R) is 70V and across an inductor (V_L) is 120V, what is the supply voltage?

• 138.92 volts

• 190 volts

• 100 volts

• 220 volts