WorksheetsIntroduction to Electrical Components
Total questions: 19
Worksheet time: 10mins
Which statement best describes the role of the consumer unit in a household electrical supply flow shown in the diagram?
It measures energy used before appliances and circuits
It distributes power and houses protective devices
It provides the incoming supply from the grid
It contains the suppliers fuse upstream of the meter
Which cable type is best for supplying an outbuilding where the run may face physical damage?
Flexible cord for portable appliances
Ring final circuit wiring in conduits
Typical twin and earth cable behind walls
Armoured cable with metal protection
Which twin and earth cable cross-section is most appropriate for a domestic shower circuit based on typical capacity and fuse ratings shown?
4.0 mm cross-section with 25A capacity
6.0 mm cross-section with 32A capacity
10 mm cross-section with 43A capacity
2.5 mm cross-section with 18A capacity
A 1.5 mm twin and earth cable is protected by a 20A fuse on a socket circuit. What is the most likely risk in this setup?
Cable stays cool under load
Fuse nuisance trips at low current
Insulation damage leading to overheating
Reduced voltage causing dimmer lighting
Which protection setup is appropriate for a typical 3 kW immersion heater installation?
16 A isolator, 10 A MCB, earth leakage relay
32 A isolator, 20 A MCB, surge protector
20 A isolator, 16 A MCB, thermal cut-out
20 A isolator, 32 A MCB, arc-fault breaker
Which statement best distinguishes trunking from conduit when protecting cables in a building?
Trunking houses multiple flexes in a rectangular duct
Trunking is a cable tray with open slots
Conduit is a flat channel fixed behind skirting
Conduit is only used for low‑voltage signal lines
Using the power triangle shown, which expression correctly calculates electrical power when current and voltage are known?
Power equals current plus voltage
Power equals voltage minus current
Power equals voltage divided by current
Power equals current times voltage
If an appliance needs 3 kW in a domestic property, what is the appropriate fuse size?
20 amp fuse recommended
13 amp fuse recommended
15 amp fuse recommended
10 amp fuse recommended
In a domestic property, an appliance has a 3 amp fuse. What is the maximum power rating of the appliance?
460 W or 0.46 kW
690 W or 0.69 kW
1,150 W or 1.15 kW
830 W or 0.83 kW
An appliance has a 5 amp fuse and requires 1.25 kW of power. What supply voltage is needed?
240 V supply required
230 V supply required
110 V supply required
120 V supply required
Which equation correctly represents Ohm’s Law relating voltage, current, and resistance?
V = I × R
R = V × I
V = R ÷ I
I = V × R
A domestic appliance is protected by a 3 A fuse on a 230 V supply. What is the appliance’s approximate resistance?
76.7 ohms
53.0 ohms
110.0 ohms
13.0 ohms
An appliance has resistance of 1200 ohms on a 230 V circuit. Which fuse rating is most appropriate?
5.0 A
13.0 A
1.2 A
0.19 A
An appliance repeatedly stops and starts when plugged in. Which action inside the plug most likely prevents this intermittent operation?
Ensure insulation sits fully in the clamp
Replace the moulded plug with rewireable
Tighten the screw-down terminals sufficiently
Loosen the screw-down terminals slightly
Which scenario requires a two-way switch instead of a one-way switch?
Controlling lights from one doorway only
Controlling lights from two separate locations
Controlling lights with a timer module
Controlling lights from a single wall dimmer
What is the primary purpose of a fused spur in a ring final circuit?
Provide local overload protection and isolation
Reduce voltage drop across long cable runs
Increase conductor cross-sectional area at outlets
Combine lighting and power circuits in one device
Which installation requires a triple pole isolator rather than a double pole?
Single-phase socket outlet connection
Basic electric shower close to unit
Standard immersion heater circuit
Boiler with fan overrun control
Which statement best describes a junction box used in domestic wiring?
Used to connect appliances directly without enclosures
Used to expose conductors for quick maintenance access
Used only outdoors to house distribution boards
Used for flex connections with no conductors visible
Which statement best explains why isolators must be lockable and clearly labelled during electrical work?
To reduce the number of consumer units
To increase the size of MCB fused spurs
To speed up routine appliance switching
To prevent accidental re-energising of circuits
