Electrician Class 2 Quiz

Electrician Class 2 Test Questions

• Test Item 19 A tong tester instrument can also be called a clip on ammeter.

• Test Item 20 A transformer core is laminated to reduce eddy current loss.

Nickel Cadmium Cell Advantages

• Long lifespan: Nickel Cadmium cells can withstand a large number of charge/discharge cycles.
• High discharge rate: They can provide a high current output for short periods.
• Wide operating temperature range: They function well in various temperatures.

Ohm's Law and Power Dissipation

• Ohm's Law: States that the current through a conductor between two points is directly proportional to the voltage across the two points, and inversely proportional to the resistance between them.
• Current calculation: Using Ohm's Law, the current flowing through a 500Ω resistor with 100V applied is 0.2 Amps (I = V/R = 100/500).
• Power dissipation: The power dissipated by the resistor is 20 Watts (P = I²R = 0.2² * 500).

Power Factor

• Definition: The power factor is the ratio of real power to apparent power in an AC circuit. It represents how effectively electrical power is being used.

Transformer Moisture Absorbent

• Silica gel: It absorbs moisture to prevent corrosion and insulation breakdown within the transformer.

Inductive Load Impact

• Inductive load with 0.8 power factor: This creates a lagging current, which can lead to increased voltage drop, reduced efficiency, and higher energy consumption in an electrical installation.

DC Motor Components

• Armature: The rotating part of a DC motor, containing the windings connected to the commutator. It acts as a conductor, inducing magnetic force in the presence of a magnetic field.
• Commutator: A segmented ring connected to the armature winding, which reverses the current direction in the armature coils at each rotation, ensuring continuous rotation.

Efficiency Types

• Ampere-hour efficiency: The ratio of the output amperes and time to the input amperes and time.
• Watt-hour efficiency: The ratio of the output power and time to the input power and time.

Fuse

• Purpose: Provides protection to an electrical circuit by interrupting current flow when it exceeds a predetermined limit, preventing damage to equipment or fire hazards.

Arcing Horns

• Lighting protection: Arcing horns, located near the transformer terminals, divert the path of a lightning strike away from the transformer windings by providing a conductive path to ground.

Discrimination

• Definition: Discrimination in electrical protection refers to selecting the correct protective device (e.g. fuse or circuit breaker) to isolate specific faults, minimizing damage to the system and ensuring the rest of the system continues to function.

Interpoles in DC Machines

• Purpose: Interpoles, situated between the main field poles, are used to improve commutation by neutralizing armature reaction fluxes, resulting in a smoother, less sparking operation.

Safe Lifting Practice

• Correct method: Maintain a firm grip, secure footing with feet placed apart, bend knees, keep back straight, and lift using leg muscles.

Motor Protection

• Requirement: Electrical motors with a rating above 0.37kW must be equipped with a motor starter.

Moving Coil Meters

• Characteristics: Moving coil meters have a linear scale and are specifically designed for DC current measurement.

Series Connections

• Current: Components connected in series will always have the same current flowing through them.

Soft Solder Composition

• Alloy: Soft solder used for electrical joints is an alloy of Tin and Lead.

Split Phase Motor

• Type: A capacitor run and start motor is an example of a split phase motor.

Temporary Installation Inspection

• Frequency: Temporary installations on construction sites need to be inspected and tested every month.