Electrical Focused Learning – Questions & Answers
Which of the following statements defines the term transducer?
Select one:
1.A device that changes a small input signal to a larger output.
2.A device that detect the presence of a material without making physical
contact.
3.A device that converts physical or chemical qualities into electrical signals.
4.A semi-conductor device, the resistance of which changes with temperature.
Right Ans - 3. A device that converts physical or chemical qualities into
electrical signals.
An increase in the Protective Earthing Conductor's resistance would have an
effect on the operation of the circuit protective device. Select from the list
what this effect could be?
Select one:
1.Protective device may not operate due to reduced fault current.
2.Protective device would operate due to increased resistance.
3.Voltage drop in the circuit would increase.
4.No change in the operation of the protective device. Right Ans - 1.
Protective device may not operate due to reduced fault current.
Which of the factors listed will limit the prospective short-circuit current in an
electrical installation?
Select one or more:
1.Circuit impedance from transformer to the electrical switchboard
2.Type of distribution switchboard installed.
3.Supply frequency
4.Impedance of the supply transformer Right Ans - 4. Impedance of the
supply transformer,
1. Circuit impedance from transformer to the electrical switchboard
Which of the following factors can determine the voltage drop in a single-
phase 230V final sub-circuit cable?
Select one or more:
1.Installation method used.
2.Length of sub-circuit cable.
3.Type of protective device fitted.
4.Load. Right Ans - 4.Load.,
, 2.Length of sub-circuit cable.
Which of the following components are used to filter the pulsating output of a
rectifier?
Select one or more:
1.Capacitor
2.Diode
3.Inductor
4.Resistor Right Ans - 4.Resistor,
1.Capacitor,
3.Inductor
How does a single-phase a.c permanently split capacitor motor differ from a
single-phase a.c capacitor start motor?
Select one:
1.Has no centrifugal switch.
2.Has two capacitors.
3.Has only one winding.
4.Has only one capacitor Right Ans - 1.Has no centrifugal switch.
A 230V 1200W class 1 single-phase electric drill is connected to a circuit
protected by a 16A type C 6kA circuit breaker.A phase to frame fault of 20 Ω
has occur on the load side of the electric drill switch. The resistance of the
protective earthing conductor is 0.5Ω and the earth fault loop impedance is
0.81Ω.Choose from the list to describe the operation of the MCB with the
given fault .
Select one:
1.The MCB will not operate.
2.The MCB will operate with its electromagnetic action.
3.The MCB will operate within 4 hours.
4.The maximum fault current is greater than the rupturing capacity of the
MCB. Therefore the safety device will be destroyed. Right Ans - 1. The MCB
will not operate.
A load requires a full load torque of 98.6Nm at 1450rpm. From the list below
of three-phase 400V a.c induction motors, select which motor would match
the load requirements for maximum efficiency?
Select one:
1.15kW
Which of the following statements defines the term transducer?
Select one:
1.A device that changes a small input signal to a larger output.
2.A device that detect the presence of a material without making physical
contact.
3.A device that converts physical or chemical qualities into electrical signals.
4.A semi-conductor device, the resistance of which changes with temperature.
Right Ans - 3. A device that converts physical or chemical qualities into
electrical signals.
An increase in the Protective Earthing Conductor's resistance would have an
effect on the operation of the circuit protective device. Select from the list
what this effect could be?
Select one:
1.Protective device may not operate due to reduced fault current.
2.Protective device would operate due to increased resistance.
3.Voltage drop in the circuit would increase.
4.No change in the operation of the protective device. Right Ans - 1.
Protective device may not operate due to reduced fault current.
Which of the factors listed will limit the prospective short-circuit current in an
electrical installation?
Select one or more:
1.Circuit impedance from transformer to the electrical switchboard
2.Type of distribution switchboard installed.
3.Supply frequency
4.Impedance of the supply transformer Right Ans - 4. Impedance of the
supply transformer,
1. Circuit impedance from transformer to the electrical switchboard
Which of the following factors can determine the voltage drop in a single-
phase 230V final sub-circuit cable?
Select one or more:
1.Installation method used.
2.Length of sub-circuit cable.
3.Type of protective device fitted.
4.Load. Right Ans - 4.Load.,
, 2.Length of sub-circuit cable.
Which of the following components are used to filter the pulsating output of a
rectifier?
Select one or more:
1.Capacitor
2.Diode
3.Inductor
4.Resistor Right Ans - 4.Resistor,
1.Capacitor,
3.Inductor
How does a single-phase a.c permanently split capacitor motor differ from a
single-phase a.c capacitor start motor?
Select one:
1.Has no centrifugal switch.
2.Has two capacitors.
3.Has only one winding.
4.Has only one capacitor Right Ans - 1.Has no centrifugal switch.
A 230V 1200W class 1 single-phase electric drill is connected to a circuit
protected by a 16A type C 6kA circuit breaker.A phase to frame fault of 20 Ω
has occur on the load side of the electric drill switch. The resistance of the
protective earthing conductor is 0.5Ω and the earth fault loop impedance is
0.81Ω.Choose from the list to describe the operation of the MCB with the
given fault .
Select one:
1.The MCB will not operate.
2.The MCB will operate with its electromagnetic action.
3.The MCB will operate within 4 hours.
4.The maximum fault current is greater than the rupturing capacity of the
MCB. Therefore the safety device will be destroyed. Right Ans - 1. The MCB
will not operate.
A load requires a full load torque of 98.6Nm at 1450rpm. From the list below
of three-phase 400V a.c induction motors, select which motor would match
the load requirements for maximum efficiency?
Select one:
1.15kW
