Electrical Circuits Quiz

How is alternating current (a.c.) described?

• A current which is constant over time

• A current which changes direction and instantaneous value with time

• A current that only changes direction but not instantaneous value

• A current that only changes instantaneous value but not direction

Answer explanation

Alternating current (a.c.) is described as a current which changes direction and instantaneous value with time.

What is the relationship between the peak voltage (Vp) and the r.m.s. voltage (Vrms) for a sinusoidally varying voltage?

• Vp = Vrms

• Vp = Vrms / √2

• Vp = √2 × Vrms

• Vp = Vrms^2

Answer explanation

The correct relationship between peak voltage (Vp) and r.m.s. voltage (Vrms) for a sinusoidally varying voltage is Vp = √2 × Vrms.

In a resistive circuit, how does the frequency of the supply affect the current in an a.c. circuit?

• The current increases with frequency

• The current decreases with frequency

• The current is unaffected by the frequency of the supply

• The current is only affected at high frequencies

Answer explanation

The current is unaffected by the frequency of the supply

What is the sum of the currents in parallel branches of a circuit?

• Equal to the smallest current in one of the branches

• Equal to the sum of the voltages across the branches

• Equal to the current drawn from the supply

• Always zero

Answer explanation

The sum of currents in parallel branches of a circuit is equal to the current drawn from the supply, as Kirchhoff's Current Law states that the total current entering a junction is equal to the total current leaving the junction.

What is the relationship between energy (E) and power (P) in an electrical circuit?

• P = E × t

• P = E / t

• P = t / E

• P = E + t

Answer explanation

Power (P) in an electrical circuit is calculated by dividing the energy (E) by the time (t), so the correct relationship is P = E / t.

Which of the following equations correctly represents the equivalence between power, voltage, and resistance?

• P = I^2 × R

• P = V × I

• P = V^2 / R

• All of the above

Answer explanation

The correct equation representing the equivalence between power, voltage, and resistance is P = I^2 × R, P = V × I, and P = V^2 / R, hence all of the above are correct.

What does a potential divider circuit consist of?

• A number of inductors connected across a supply

• A number of resistors, or a variable resistor, connected across a supply

• A number of capacitors connected in series

• A single resistor connected to a voltage source

Answer explanation

A potential divider circuit consists of a number of resistors, or a variable resistor, connected across a supply, allowing for voltage division.

What is the e.m.f. of a source defined as?

• The resistance offered by the source

• The current flowing through the source

• The electrical energy supplied to each coulomb of charge when no current is drawn

• The voltage drop across the source

Answer explanation

The e.m.f. of a source is defined as the electrical energy supplied to each coulomb of charge when no current is drawn.

What is the unit of capacitance?

• Ohm

• Volt

• Farad

• Coulomb

Answer explanation

The unit of capacitance is Farad, which is denoted by the symbol F. Capacitance is the ability of a system to store an electric charge.

What is the energy stored in a capacitor given by?

• E = QV

• E = 1/2 QV

• E = 1/2 CV^2

• E = 1/2 Q^2/C

Answer explanation

The energy stored in a capacitor is given by the formula E = 1/2 CV^2, which represents the energy stored in the electric field between the plates of the capacitor.