2b-Mains electricity Flashcards
What type of current is used in mains electricity?
A: Mains electricity uses Alternating Current (AC), which means the current direction changes periodically.
What is the frequency and voltage of mains electricity in the UK?
A:
Frequency: 50 Hz (50 cycles per second)
Voltage: 230 V
Alternating Current (AC):
Current constantly changes direction (used in mains electricity).
Direct Current (DC):
Current flows in one direction only (used in batteries).
What are the three wires in a plug and their functions
Live wire
Live Wire
colour :Brown
Function: Carries high voltage (230 V) from mains supply.
What are the three wires in a plug and their functions
Neutral wire
Neutral Wire
color :Blue
Function: Completes the circuit and carries current back to mains.
What are the three wires in a plug and their functions
Earth wire
Earth Wire
color : Green/Yellow
Function: Safety wire that prevents electric shock.
What is the role of the earth wire?
A: The earth wire provides a low resistance path to the ground, preventing electric shock in case of a fault.
Why are plug casings made of plastic?
A: Plastic is an insulator, preventing electric shock.
What is a fuse and how does it work?
: A fuse is a thin wire that melts when current exceeds a certain limit, breaking the circuit and preventing damage.
How do you choose the correct fuse rating?
A: The fuse should be slightly higher than the normal operating current.
Example: If a device operates at 3 A, use a 5 A fuse, not a 13 A fuse.
What is a circuit breaker and how does it work?A:
A circuit breaker is an automatic switch that trips when excessive current flows, stopping the circuit and preventing damage.
Why are circuit breakers better than fuses?
A: They react faster, can be reset, and do not need replacing like fuses.
Energy Equation:
E=Pt (Energy = Power × Time)
Alternative Power Equations:
(Power = Current² × Resistance)
(Power = Voltage² ÷ Resistance)
Q: What are the main dangers of electricity?A:
Electric shock: Can cause severe injury or death.
Overheating wires: Can lead to fires.
Short circuits: Can cause sparks or damage to appliances.
What are the key safety precautions when using electricity?
A:
Use fuses/circuit breakers to prevent excessive current.
Insulation of wires to prevent contact with live wires.
Do not overload sockets to prevent overheating.
Use an earth wire for appliances with metal cases.
Turn off power before repairs to prevent electric shock.
Practical: Investigating Electrical Safety
Measuring Power Consumption
Method: Use a voltmeter and ammeter to measure voltage and current in a circuit.
Observation: Use P = VI to calculate power usage.
Practical: Investigating Electrical Safety
Testing Fuse Ratings
Method: Connect different fuses to a circuit with a variable resistor and increase the current until the fuse blows.
Observation: Fuses blow at their rated current, cutting off power.
