Electricity in the home Flashcards
(17 cards)
Why is the current provided by a cell called a direct current (d.c.)?
It only flows in one direction.
What is an alternating current (a.c.)?
Current that repeatedly reverses direction.
What kind of current is supplied by mains electricity?
Alternating current.
What is the frequency and voltage of mains electricity?
50 Hz, 230 V.
What is the function of the live wire in a three-core cable?
Carries the alternating potential difference from the supply.
What colours are the live, neutral, and earth wires?
Live = brown, neutral = blue, earth = green and yellow stripes.
What is the function of the neutral wire in a three-core cable?
Completes the circuit.
What is the function of the earth wire in a three-core cable?
Safety wire to stop the appliance becoming live when there is a fault.
When is there a current in the earth wire?
When there is a fault.
Why is the live wire dangerous?
Provides a large p.d. that would cause a large current to flow through a person if they touched it.
What is the National Grid?
Nationwide network of cables and transformers that link power stations to customers.
What are step-up transformers used for in the National Grid?
Increase the p.d. from the power station to the transmission cables.To deprecate the current therefore decrease energy lost as heat to the surroundings
What are step-down transformers used for in the National Grid?
Decrease the p.d. from the transmission cables to the mains supply in buildings so that it is safe to use.
How does having a large potential difference in the transmission cables help to make the National Grid an efficient way to transfer energy?
Large p.d. means a small current is needed to transfer the same amount of power, small current in the transmission cables means less electrical power is wasted due to heating.
What are the units for power, current, potential difference, and resistance?
Watts (W), amps (A), volts (V), ohms (Ω).
What type of current does a cell or battery produce?
Direct current(produced by direct p.d.)
What does alternating current mean?
The current repeatedly frequently reverses direction(produced by an alternating p.d.) used to my main electricity
