Domestic Uses And Safety Flashcards
How is current supplied by cells and batteries and what does it mean
Directly, (direct current) always flows in the same direction
How does time affect p.d and current change in a bulb when direct current?
No change, always the same
How is current supplied by main socket and what does it mean
Alternating, constantly change direction (in the circuit)
What is frequency and voltage in the UK
Frequency=50hz
Voltage=230V
How does voltage affect currents flow in a alternating current, and how many times does this change occur per second?
When voltage is positive current flows in one direction and when negative it flows in the opposite direction. 50 times per second
What do each wires do?
Live=provides alternating voltage from power supply
Neutral=completes circuit
Earth=carries current if there is a fault
How does a earth wire work?
When there is a fault in circuit, current will flow in it
The earth wire has a lower resistance than a human body
More current will flow in the wire than in the human
What is the fuse connected to?
Live wire
How do fuses work?
Large current flows through fuse
Maximum rating of fuse is exceeded
Fuse blows
Fuses reduce risk of electrical fires only and not electrocution
How do circuit breakes work (magnetically activated)?
Use an electromagnet to detect overcurrent
When current exceeds the safe limit, the coil generates a strong magnetic field
This attracts a metal armature
This triggers the circuit breaker to open, isolating the fault
Quick response minimises damage and fire risks
After fixing the fault, manual reset is possible
What appliances do not need an earth wire?
Double insulated
Why do double insulated appliances not need an earth wire?
Designed with two layers of insulation and do not have exposed metal parts
They are classified as class 2 appliances
No earth wire is needed
