Electrical Science Paper B2

The opposition to current flow in a.c. resistive circuit is called:

• Resistance

• Inductance

• Reactance

• Impedance

The opposition to current flow in a.c. capacitive or inductive current is called:

• Resistance

• Inductance

• Reactance

• Impedance

The total opposition to current flow in any a.c. circuit is called:

• Resistance

• Inductance

• Reactance

• Impedance

An a.c. series circuit has an inductive reactance of 4 Ω and a resistance of 3 Ω. The impedance of this circuit will be:

• 5 Ω

• 7 Ω

• 12 Ω

• 25 Ω

An a.c. series circuit has a capacitive reactance of 12 Ω and a resistance of 9 Ω. The impedance of this circuit will be:

• 3 Ω

• 15 Ω

• 20 Ω

• 108 Ω

The inductive reactance of a 100mH coil when connected to a 50Hz supply will be:

• 5 Ω

• 20 Ω

• 31.42 Ω

• 31.42 KΩ

The capacitive reactance of a 100 μF capacitor when connected to a 50 Hz supply will be:

A circuit with poor power factor causes:

• The supply voltage to fail

• The supply voltage to increase

• More current consumption from the supply

• Less current consumption from the supply

If uncorrected, poor power factor means the circuit conductors have to be:

• Made smaller

• Made bigger

• Made longer

• Made shorter

Calculate the design current in a domestic single phase supply that has a power rating of 5 KW and operates with a power factor of 0.8.

• 17.39 A

• 27.17 A

• 46 A

• 36.8 A