P5 - Electricity in the Home Flashcards
Define DC
Direct Current - current that flows in one direction in a circuit
y = c (+ve)
Define AC
Alternating Current - current that constantly changes direction
y = sin x
Why is AC used for mains electricity?
AC is more efficiently transferred over large distances.
What is a CRO
Cathode Ray Oscilloscope
An instrument used to display electrical signals onto a graph.
What is the frequency and voltage of UK mains electricity?
50 Hz
230V
What are the names and colours of UK electricity wires?
live - brown
neutral - blue
earth - striped green and yellow
What is the purpose of the earth wire?
To increase safety. It creates a shorter path for electricity to flow in appliances with metal casings to prevent electrocution.
define a short circuit
when current takes an unintended shortest path through a circuit and doesn’t flow through the components
How does a fuse work?
A fuse has a wire with a known resistance. If the current is too high it will melt the wire and cause the circuit to break.
How does a circuit breaker work?
It measures the difference in current between the live and neutral wires. If the difference is too great, an electromagnetic switch opens and breaks the circuit.
Name 2 reasons why circuit breakers are better than fuses
- They break a circuit faster
- They can be used indefinitely
What does a step-up transformer do?
It increases the voltage and decreases the current
+ volts, - amps
What does a step-down transformer do?
It decreases the current and increases the voltage
-volts, +amps
Why are mains electricity at high voltage and low current
A lower current is more efficient because there is less dissipation through heating
formula power
using energy
power = energy / time
P = E / t
