Generating electricity Flashcards
What is a magnetic field?
A region where magnetic materials and also wires carrying currents experience a force acting on them
Where do the arrows go from in a magnet diagram?
From the North Pole to the South Pole
What is the shape of the magnetic field of a straight current-carrying wire?
The field is made up of concentric circles with the wire in the centre
Why are wire coils more reinforced in magnetic fields?
Because the two magnetic fields of the wires meet in the middle, reinforcing both fields
If there were many coils many fields would meet and reinforce, making it more sturdy
Is the magnetic field strong or weak in a coil of wire?
Strong and uniform, running the length of the coil
What is the magnetic field like outside a coil?
Like a bar magnet
What happens to the magnetic field if the current is reversed in a coil?
The north and south swap ends
How can you increase the strength of the magnetic field around a coil (solenoid)?
Adding a magnetically ‘soft’ iron core though the middle of the coil
This turns it into an electromagnet
What is a magnetically soft material?
A material that magnetised and demagnetises easily so as soon as you turn off the current through the solenoid (coil) the magnetic field disappears
What happens when you put a current carrying wire between magnetic poles?
The two magnetic fields affect one another and a force on the wire is made
What is the force if a current carrying wire runs along the magnetic field lines?
Nothing, as it does not break any magnetic field lines.
Is the force strong or weak when a current carrying wire is 90 degrees to a magnetic field?
It is at its fullest
What direction does the force travel on a current carrying wire in a magnetic field?
The same direction relative to the magnetic field of the magnets and the direction of the current in the wire (Left hand rule)
How do you find the way the force acts on a current carrying wire in a magnetic field?
Using the left hand rule
thuMb - Motion
First finger - Force of magnet
seCond finger - Direction of conventional current
What speeds up an electric motor?
More current
More turns on the coil
Stronger magnetic field
A soft iron core in the coil
How does an electric motor work?
A coil is on a spindle and has a current running through it with a magnetic field
One force goes up and one goes down, making the coil spin
The coil swaps the contacts every half a turn to keep the motor rotating in the same direction
How can the direction of a motor be reversed?
By swapping the polarity of the electricity supply or swapping the magnetic poles
What do practical motors (Eg a drill) have instead of simple electrical motors to generate electricity?
They have pole pieces which are so curved they form a hollow cylinder. The coil spins inside the cylinder.
They stick anything to the end of the pole and it spins
How do AC generators work?
Use a turbine to rotate a coil in a magnetic field (like a motor)
As the coil spins a current is induced in the coil. This current changes direction every half turn
Instead of a split-ring communicator, they have slip rings and brushes so the contacts don’t spin every half turn
This means they produce AC voltage
How do Dynamo generators work?
They rotate the magnet instead of the coil
This causes the field through the coil to swap every half turn also, so the output is the same as a normal generator
Why do you need transformers in power lines?
Without them, the current in the wire would be high and energy would be lost through heat.
However, large voltage means small current, so it’s boosted up to 400,000V to prevent energy loss
What is an isolating transformer?
A transformer that is equal on both sides, and reduces mains electricity for safety
How does an isolating transformer protect you?
It makes it so you’re not directly touching the mains so there’s no way current can flow through you
How do nuclear power stations work?
Uranium atoms are split, generating loads of heat which power a turbine
What is nuclear fusion?
Two nuclei combine to create a larger nucleus
Why are people trying to create fusion reactors?
Fusion creates the most energy
What are the challenges for fusion reactors?
It needs to be really hot and nearly no material can withstand the heat
