Capacitance in AC Circuits

What is the relationship between charge (Q), voltage (V), and capacitance (C) in a capacitor?

• Q = V + C

• Q = V.C

• Q = V - C

• Q = V/C

What happens to a capacitor when it is connected across an a.c. supply?

• It neither charges nor discharges.

• It explodes.

• It only charges without discharging.

• It charges and discharges with opposite polarity.

What is the formula for capacitive reactance (Xc)?

• Xc = V + I

• Xc = 2πfC

• Xc = 1/(2πfC)

• Xc = V/I

How does the frequency of the supply affect the capacitive reactance?

• No effect

• Inversely proportional

• Frequency doubles the reactance

• Directly proportional

What is the energy stored in a capacitor given by?

• Q = 1/2 . C . V^2

• E = 1/2 . C . V

• E = C . V^2

• E = 1/2 . C . V^2

What is the phase relationship between the current and voltage in a capacitive circuit?

• Current leads voltage by 90°

• Current leads voltage by 180°

• Current lags voltage by 90°

• Current and voltage are in phase

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

• By multiplying resistance and capacitance

• By dividing resistance by capacitance

• By using Pythagoras theorem

• By simple arithmetic addition

What does the power factor (pf) indicate in a circuit?

• The ratio of resistance to impedance

• The phase difference between voltage and current

• The efficiency of the circuit

• The total power consumed by the circuit

What is the effect of increasing the frequency on the charge flow into the capacitor?

• Charge flow decreases

• Charge flow remains constant

• Charge flow increases

• Charge flow stops

What property allows current to flow in a capacitor despite it having infinite resistance in a d.c. circuit?

• Magnetic reactance

• Resistive reactance

• Capacitive reactance

• Inductive reactance