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Electrical Concepts and Questions Study Notes

Cable Current Carrying Capacity

  • Question 47: What happens to the cable current carrying capacity when cables are bundled together, such as when tied along a catenary wire?

    • Answer: c. It decreases.

Insulation Resistance

  • Question 48: What is the minimum insulation resistance reading allowable between motor windings?

    • Options:

    • a. 0.01 ΜΩ

    • b. 0.5 ΜΩ

    • c. 1 ΜΩ

    • d. 10 Ω

    • Correct Answer: c. 1 ΜΩ

Cables for Domestic Wiring

  • Question 49: Which of the following cables would be best suited for general fixed wiring such as power circuits in a domestic environment?

    • Options:

    • a. Normal duty flexible cable

    • b. Circular TPS

    • c. Neutral screen cable

    • d. Flat TPS

    • Correct Answer: b. Circular TPS

HRC Fuse Current Rating

  • Question 50: If an HRC fuse operates ('blows') at 20A and has a utilization category (fusing factor) of 1.25, the current rating of the fuse is:

    • Options:

    • a. 12.5 A

    • b. 20 A

    • c. 10 A

    • d. 16 A

    • Correct Answer: a. 12.5 A

Current Flow in Circuits

  • Question 41: What is the current flow through R5?

    • Options:

    • a. 1 A

    • b. 1.5 A

    • c. 2 A

    • d. 2.5 A

    • Correct Answer: b. 1.5 A

Cost Calculation for Electrical Devices

  • Question 42: What would be the cost of using a 4kW heater for 5 hours per day for 6 days if the unit cost per kWh is $0.35?

    • Options:

    • a. $33

    • b. $92

    • c. $23

    • d. $42

    • Correct Answer: d. $42

Magnetic Properties

  • Question 43: Which of the following is best described as 'the faces of a magnet where the lines of force leave and enter?'

    • Options:

    • a. Magnetic flux

    • b. Magnetic poles

    • c. Magnetic field strength

    • d. Flux density

    • Correct Answer: b. Magnetic poles

Frequency of Sine Waves

  • Question 44: In a 0.5-second period, a sinewave has 30 complete cycles. Its frequency is therefore:

    • Options:

    • a. 60 Hz

    • b. 15 Hz

    • c. 20 Hz

    • d. 10 Hz

    • Correct Answer: a. 60 Hz

Ohm's Law and Circuit Current

  • Question 45: If both the voltage and resistance of a circuit are doubled, what would happen to the current flow in the circuit?

    • Options:

    • a. It would be double the original value

    • b. It would be half the original value

    • c. It would increase by four times the original value

    • d. It would not change

    • Correct Answer: d. It would not change.

Supervision of Trainees

  • Question 46: According to the Electrical Workers Registration Board's Supervision Procedures for Trainees, the supervisor of apprentices and trainees must take responsibility for ensuring that:

    • Options:

    • a. The trainee's work is completed in a timely manner.

    • b. The work is completed in accordance with employer's needs.

    • c. The trainee is not allowed to work outside of their supervisor's limits.

    • d. The trainee only takes the allocated breaks

    • Correct Answer: a. The trainee's work is completed in a timely manner.

Circuit Analysis

  • Question 37: What is the total resistance of the parallel circuit containing R1 (20 Ω) and R2 (30 Ω)?

    • Options:

    • a. 50 Ω

    • b. 12 Ω

    • c. 15 Ω

    • d. 20 Ω

    • Correct Answer: c. 15 Ω

  • Question 38: What is the total resistance of the entire circuit?

    • Options:

    • a. 12 Ω

    • b. 24 Ω

    • c. 60 Ω

    • d. 115.50 Ω

    • Correct Answer: a. 12 Ω

  • Question 39: What is the total current drawn by the circuit?

    • Options:

    • a. 1 A

    • b. 4 A

    • c. 6 A

    • d. 8 A

    • Correct Answer: c. 6 A

  • Question 40: What is the volt drop across R3 (10.5 Ω)?

    • Options:

    • a. 22 V

    • b. 32 V

    • c. 42 V

    • d. 52 V

    • Correct Answer: c. 42 V

Electromagnets and Electrical Components

  • Question 30: Which of the following is a device that uses an electromagnet to operate a trip mechanism if there is a short circuit in a circuit?

    • Options:

    • a. Motor

    • b. Generator

    • c. Solenoid

    • d. MCB (Miniature Circuit Breaker)

    • Correct Answer: d. MCB

  • Question 31: Which of the following best describes an electromagnet?

    • Options:

    • a. A magnet that is naturally magnetic and holds its magnetism indefinitely

    • b. A magnet that gets its magnetism from a coil of wire with an electrical current flowing through it.

    • c. A magnet that gets its magnetism from a coil of wire with no current flowing through it

    • d. A magnet that stays magnetized once a coil of wire with an electric current flowing through it is turned on and then off.

    • Correct Answer: b. A magnet that gets its magnetism from a coil of wire with an electrical current flowing through it.

  • Question 32: Which of the following is equivalent to 0.6 A?

    • Options:

    • a. 6 mA

    • b. 60 mA

    • c. 600 mA

    • d. 6000 mA

    • Correct Answer: c. 600 mA

  • Question 33: The unit of current is:

    • Options:

    • a. Volt

    • b. Ampere

    • c. Ohms

    • d. Amp-meter

    • Correct Answer: b. Ampere

  • Question 34: Which of the following would be a typical use for mica in the electrical industry?

    • Options:

    • a. Cable cores

    • b. Motor brushes

    • c. Heating element supports

    • d. Earth bars

  • Question 35: The total resistance of resistors in parallel will always be:

    • Options:

    • a. Less than the lowest resistor

    • b. Greater than the lowest resistor

    • c. Equal to the lowest resistor

    • d. The addition of all resistors

    • Correct Answer: a. Less than the lowest resistor

  • Question 36: Which of the following best describes a conductive fluid that is used to move ions between the plates of a cell?

    • Options:

    • a. The anode

    • b. The electrode

    • c. The electrolyte

    • d. The cathode

    • Correct Answer: c. The electrolyte

Electrical Calculations

  • Question 27: Calculate the length of side B of the right-angled triangle given the following values:

    • A = 20

    • C = 50

    • Options:

    • a. 22.36

    • b. 38.56

    • c. 45.83

    • d. 55.32

  • Question 28: For the right-angled triangle below, calculate the length of the side marked 'x' if opposite is replaced with x, angle = 30º.

    • Options:

    • a. 3

    • b. 4

    • c. 5

    • d. 6

    • Correct Answer: c. 5

  • Question 29: Calculate the power dissipated in a 12 V DC circuit given that the current flowing is 0.5 A.

    • Options:

    • a. 12 W

    • b. 6 W

    • c. 24 W

    • d. 12.5 W

    • Correct Answer: a. 6 W

Earth Continuity Tests

  • Question 21: What is the maximum resistance permitted when carrying out the earth continuity test on a class 1 appliance?

    • Options:

    • a. 1 Ω

    • b. 0.5 Ω

    • c. 10 Ω

    • d. 100 Ω

    • Correct Answer: a. 1 Ω

Circuit Isolation

  • Question 22: Which type of meter would you use to confirm isolation of a circuit?

    • Options:

    • a. Ohmmeter

    • b. Ammeter

    • c. Voltmeter

    • d. Wattmeter

    • Correct Answer: c. Voltmeter

  • Question 23: Why will an RCD trip when there is a leakage to earth from the phase conductor?

    • Options:

    • a. The current in the neutral conductor passing through the RCD will be greater than the current in the phase conductor.

    • b. The current in the neutral conductor passing through the RCD will be less than the current in the phase conductor.

    • c. The current in the neutral conductor passing through the RCD will be the same as the current in the phase conductor.

    • Correct Answer: a. The current in the neutral conductor passing through the RCD will be greater than the current in the phase conductor.

  • Question 24: Which of the following devices contains both a magnetic coil and a bi-metal strip?

    • Options:

    • a. MCB

    • b. RCD

    • c. Overload

    • d. Fuse

    • Correct Answer: a. MCB

Inverse Time-Current Characteristics

  • Question 25: What is meant by the term 'inverse time-current characteristics' in relation to protective devices?

    • Options:

    • a. The higher the current, the longer it takes for the protection device to operate.

    • b. More current is needed to operate the device.

    • c. As the current increases through the protection device, the time taken to operate decreases.

    • d. Less current is required to operate protective devices.

    • Correct Answer: c. As the current increases through the protection device, the time taken to operate decreases.

  • Question 26: Ammeters should always be connected in:

    • Options:

    • a. Parallel with the load.

    • b. Series-parallel with the load.

    • c. Series with the load.

    • d. Doesn't matter, as long as it is connected across the load.

    • Correct Answer: c. Series with the load.

Tool Identification and Safety Measures

  • Question 14: What is the function of a scale used on a plan?

    • Options:

    • a. It allows a large area to be represented on a relatively small area of paper or screen.

    • b. It gives the reader extra information such as environmental conditions.

    • c. It identifies what the symbols on the plan represent.

    • d. It informs the reader how the plan is to be implemented.

    • Correct Answer: a. It allows a large area to be represented on a relatively small area of paper or screen.

  • Question 15: Which of the following best describes a "make" contact?

    • Options:

    • a. Normally closed contacts that open when operated.

    • b. Normally open contacts that close when operated.

    • c. How contacts sit when the circuit is de-energised.

    • d. A contact that has both a normally open contact and a normally closed side.

    • Correct Answer: b. Normally open contacts that close when operated.

  • Question 16: What does the second number of an IP rating tell you?

    • Options:

    • a. Level of protection against water.

    • b. Level of protection against solid objects.

    • c. Level of protection against gases.

    • d. Level of protection against electric shock.

    • Correct Answer: b. Level of protection against solid objects.

  • Question 17: Why are secure, well-made cable terminations and connections important?

    • Options:

    • a. If they are not, the connection may become low resistance and cause an arc fault.

    • b. If they are not, the connection may become short-circuited and cause an arc fault.

    • c. If they are not, the connection may become zero resistance and cause an arc fault.

    • d. If they are not, the connection may become high resistance and cause an arc fault.

    • Correct Answer: d. If they are not, the connection may become high resistance and cause an arc fault.

Health and Safety Responsibilities

  • Question 18: Which of the following are employees responsible for, under the Health and Safety at Work Act (2015)?

    • Options:

    • a. Maintaining a health and safety register to report all hazards and incidents to their employers.

    • b. Taking reasonable care that their actions do not threaten the health and safety of others.

    • c. Addressing only those health and safety risks that are new or have arisen since they began employment.

    • d. Eliminating all safety risks from the workplace.

    • Correct Answer: b. Taking reasonable care that their actions do not threaten the health and safety of others.

  • Question 19: If a cable run goes through thermal insulation for at least 200mm, what would happen to its current carrying capacity?

    • Options:

    • a. It will decrease.

    • b. It will stay the same.

    • c. It will increase.

    • Correct Answer: a. It will decrease.

Insulation Resistance Based on Length

  • Question 20: A 500-meter cable has an insulation resistance of 500 MΩ. What would the insulation resistance of the cable be if it were shortened to 100 meters?

    • Options:

    • a. 250 MΩ

    • b. 500 MΩ

    • c. 1500 MΩ

    • d. 2500 MΩ

    • Correct Answer: b. 500 MΩ.