Electrical Installation mock part 2

State three human resource factors that will require monitoring during an electrical installation project.

• Team skills, availability, and conflict resolution

• Budget, project timeline, and equipment

• Client satisfaction, supplier contracts, and external risks

• Weather conditions, site accessibility, and material quality

Answer explanation

Team skills, availability, and conflict resolution are human resource factors that require monitoring during an electrical installation project.

Which of the following is NOT a principle of operating a wind turbine?

• Wind Turbine converts kinetic energy from the wind into mechanical power.

• Gear box is used to increase the rotational speed from the turbine to the generator.

• Generator converts mechanical energy into electrical energy.

• Wind Turbine operates solely on solar power.

Answer explanation

The correct choice is 'Wind Turbine operates solely on solar power' because wind turbines do not operate on solar power but rather convert wind energy into mechanical or electrical power.

A 0.318 H inductor has a resistance of 20 Ω and is connected in series with a capacitor of 38.9 μF. They are connected to an AC 230 V supply at 50 Hz. Calculate the circuit’s power factor.

• 0.95

• 0.85

• 0.75

• 0.65

Answer explanation

The power factor can be calculated using the formula: power factor = resistance / sqrt(resistance^2 + (inductance - capacitance)^2). Substituting the given values, we get power factor = 20 / sqrt(20^2 + (0.318 - 38.9e-6)^2) = 0.85.

When a voltage of 110 V is applied to a circuit, a current of 20 A flows at a power factor of 0.95. Calculate the kVA.

• 2.31 kVA

• 22 kVA

• 23.16 kVA

• 11 kVA

Answer explanation

To calculate kVA, use the formula kVA = V x I x PF / 1000. Plugging in the values, kVA = 110 x 20 x 0.95 / 1000 = 23.16 kVA. Therefore, the correct answer is 23.16 kVA.

An inductor has an inductive reactance of 4 kΩ when it is connected across a 24 V, 50 kHz AC supply. Calculate the supply current.

• 0.006 A

• 6 mA

• 60 mA

• 600 mA

Answer explanation

The supply current can be calculated using Ohm's Law: I = V / X, where V is the voltage (24 V) and X is the inductive reactance (4 kΩ). Therefore, I = 24 V / 4 kΩ = 6 mA.

How does the wound rotor on an AC induction motor achieve a high starting torque?

• By increasing the resistance in the rotor circuit

• By decreasing the resistance in the rotor circuit

• By maintaining a constant resistance in the rotor circuit

• By eliminating the rotor circuit

Answer explanation

Increasing the resistance in the rotor circuit of a wound rotor on an AC induction motor helps achieve a high starting torque by controlling the flow of current and increasing the torque output.

Which of the following are the three principles of space heating?

• Conduction, Convection, Radiation

• Conduction, Insulation, Ventilation

• Radiation, Insulation, Convection

• Ventilation, Radiation, Conduction

Answer explanation

The three principles of space heating are Conduction, Convection, and Radiation, making the correct answer choice Conduction, Convection, Radiation.

Describe the operating principle of a thermostat in an immersion heater.

• It converts electrical energy into heat energy.

• It measures the temperature of the water and turns the heater off when it reaches a set point.

• It prevents water from freezing.

• It heats the water by direct contact.

Answer explanation

The thermostat in an immersion heater measures the temperature of the water and turns the heater off when it reaches a set point, ensuring the water does not overheat.

State the earthing arrangement shown in Figure 1 and identify the parts labelled X and Y.

Determine a suitable type and nominal rating of protective device for a single-phase circuit supplying a total loading of 4000 W discharge lighting.

• Type B, 20 A

• Type C, 16 A

• Type D, 25 A

• Type B, 25 A