P5 Electricity in the Home Flashcards
What are the two types of current
Alternating current
Direct current
What type of current is the main
Alternating
What does DC stand for
Direct current
What does AC stand for
Alternating current
Where will you find direct current
A cell or battery
What is direct current
current that flows in one direction, it is either positive or negative and found in batteries and cells
What would an oscilloscope graph look like for direct current
A straight line
What is the voltage for the mains supply
230V
What is the frequency for the mains supply
50Hz
What is alternating current
A current where the electrons move in alternating directions while moving around the circuit, fluctuating 50 times per second between positive or negative
What would an oscilloscope graph of alternating current look like
A wiggly line going above and below the 0V line
What colour is the live wire
brown
What is the live wire
The wire which the electricity enters the appliance though, after the fuse
What colour is the neutral wire
blue
What is the neutral wire
It is the wire that completes the circuit, the current comes back into the plug through it
What colour is the earth wire
Yellow and green
What is the earth wire
it is the safety wire, making appliances safer to touch
When is the earth wire needed
For appliances with metal casing
How does the earth wire make appliances safer
- the earth wire carries free electrons (in the appliances metal casing) down to earth
- the prevents electric shocks and does not affect the circuit
What is A
The live wire
What is B
Fuse
What is C
Cable grip
What is D
Outer insulation
What is E
Neutral wire
What is F
earth wire
What is the core of a wire made from
Copper
What insulator do the wires have
A coloured plastic coating
Why is the cable surrounded by rubber
Because rubber is an insulator and makes it safe to touch
Why does the plug have a plastic coating
To insulate the plug making it safe to touch
What is the purpose of a fuse
A fuse is a thin wire that will melt from the heating affect of the current, to stop the circuit
What is a disadvantage of a fuse
It cannot be reused
What is the advantage of a circuit breaker
It can be used again and again
What does energy transferred depend on
power
What are the three power equations
P = energy / time
P = current^2 x resistance
P = current x voltage
Define potential difference (voltage)
voltage is the amount of energy carried per charge
Define current
The rate of flow of charge
What is the national grid
It is a giant system of cables and transformers that covers the UK and connects power stations to consumers
What is the potential difference like in the national grid
High
What is the current like in the national grid
Low
What do step up transformers do
Increase the voltage to 400,000V
What do step down transformers do
Decrease the voltage to 230V
Why do power stations run below their maximum power output
So there’s space capacity to cope with a high demand
Why does the national grid have a low current
To keep the heating affect as low as possible so no energy is wasted
Why is there a step down trasformer
So that electricity is safer to use and so it doesn’t blow the appliances
Are transformers efficient prove it
Yes
power in primary coil = power in secondary coil
What is the average voltage for DC
1.5V
Why are the pins on a plug made of Brass
- it is difficult to bend ~ strong
- very good electric conductor
