Mains electricity Flashcards
What is AC, and what is its current and frequency in mains electricity?
AC is alternating current, which repeatedly flows back & forth at 230 V with a frequency of 50 Hz in mains electricity
What is DC?
DC is direct current, which only flows in one direction
What uses AC and what uses DC?
- Mains electricity uses AC
- Batteries use DC
How do you work out frequency?
1 divided by time period
What do AC and DC look like on an oscilloscope?
- AC gives a regular repeating wave
- DC gives a flat line
What potential hazards regarding electricity can occur in the home?
- Long or frayed cables
- Water near sockets
- Damaged plugs
- Cables in contact with something hot or wet
- Too many plugs in one socket
- Appliances without covers on
What are the wires in a plug called, where are they located and what are their corresponding colours?
- Neutral- blue- bottom left
- Earth- green and yellow- middle
- Live- brown- bottom right
Aside from wires, what else do you need in a plug?
- Fuse
- Cable grip
What is a feature of the live wire?
It alternates between positive and negative voltage
What is a feature of the neutral wire?
It is always at 0v
What is the fuse?
A safety device which melts if too much current goes through the circuit, to break the circuit if there is a fault
What size fuse should you always have compared to the current flowing through?
It should be just above the normal operating current
What is the function of the earth wire?
If a fault develops when the live wire touches the metal case of an appliance, current surges down the earth wire to the ground, melting the fuse, breaking the circuit. The appliance is now isolated, preventing electrocution, fire or damage to the appliance
What does a circuit breaker do?
When they detect a surge in current, they break the circuit by opening a switch
What is an advantage and a disadvantage of a circuit breaker over a fuse?
- Can easily be reset after it breaks unlike a fuse, breaks circuit quicker than a fuse
- More expensive
What is one example of a circuit breaker?
A Residual Current Circuit Breaker (RCCB), which can detect tiny changes in current by detecting the difference between the live and neutral wire so can cut current off very quickly
How do you determine whether an appliance is efficient?
An appliance is efficient if it wastes less energy e.g. light-emitting diodes are more efficient than filament bulbs
What happens to the electrical energy when current flows through something?
When a current flows through something, resistance means electrical energy is transferred into heat energy. The bigger the voltage and current, the more heat is produced
What is potential difference?
Energy transferred per unit of charge
What happens when an electrical charge goes through change in potential difference?
Energy is transferred
What happens to charge at the power source?
At power source, energy is supplied, raising the charge through a potential
What happens to charge at components?
At components, the charge gives up its energy, falling through potential
What happens as the change in potential difference increases?
More energy is transferred for a given amount of charge passed through the circuit
What effect does the size of the voltage of a battery have on energy and charge?
Batteries with bigger voltages will supply more energy for every coulomb of charge which flows around it because charge is raised up higher at the start and more energy will be dissipated
