Magnets (paper2) Flashcards
What is the national grid
A system of wires and cables
What happens when electricity flows through a wire
It gets warm
Where is there significant energy loss in the national grid
In the transmission lines
If the voltage of electricity is increased what decreases
The current
When the current is smaller less what is transferred
Energy
What happens when less energy is transferred
Efficiency is improved
What kilo-voltage do power stations produce electricity at
25kV
What changes the 25kV to 400kV
Transformers
What is reduced before being sent into factories and buildings
The voltage
What does a step up transformer do
It increases the voltage and decreases the current at the same time
What does a step down transformer do
Decreases voltage and makes current higher
What is a transformer made up of
Two coils of insulted wire wound onto an iron core
Is there an electrical connection between the two coils of wire
No
Where is electricity supplied to in a transformer
The primary coil
How many turns are there in the primary coil
5 turns
How many turns in secondary coil
10 turns
What’s the voltage in the primary coil
10V
What’s the voltage in the secondary coil
20V
What type of current do transformers use
Alternating current
What does the alternating current in the primary coil create
A continuously changing magnetic field
What does the iron core carry
The magnetic field into the secondary coil
What does the changing magnetic field induce
A changing potential difference in the secondary coil
Where is the potential difference greater
In the secondary coil as it has more coils
What’s the potential difference in the transformer equation
PD across primary coil divided by PD across secondary coil is equal to the number of turns in the primary coil divided by number of turns in secondary coil
