Electromagnetism Key Sentences Flashcards
1
Q
What does a magnetic field line show?
A
A magnetic field line shows the direction of ‘free’ North Pole a compass would point
2
Q
3 key sentences for motor
A
- current goes around the coil
- if a current goes through a wire in a magnetic field it feels a force.
- one side of the coil the force is up and it is down on the other side: therefore the coil rotates.
3
Q
How do you find out the direction of force (on a motor)?
A
Direction of force can be understood with the left hand rule.
First finger- field
Second finger-current
Thumb-force
4
Q
Loudspeaker key sentences
A
- When a current flows through the coil it creates a magnetic field.
- The magnetic field in the coil either attracts it repels the permanent magnet.
- The coil moves in and out and makes the diaphragm vibrate.
- The vibration in the diaphragm makes the air vibrate which creates sound.
5
Q
Key sentence for electromagnetic induction
A
If a wire experiences a change in magnetic field a current is induced.
6
Q
Key sentences for a generator
A
- If a wire experiences a change in magnetic field a current is induced.
- If the coil is rotated in a magnetic field a current is induced.
- The output current is an alternating current.
7
Q
Key sentences for transformers
A
- If a current passes through a wire a magnetic field is formed.
- If an a.c current is passed through the primary coil a changing magnetic field is induced.
- The iron coil strengths the magnetic field.
- A secondary coil experiences a changing magnetic field so a current is induced.
- Transformers can be used to step-up or step-down the voltage.
8
Q
Key sentences for motor effect
A
- When a current lasses through a wire in a magnetic field e.g loudspeaker
- If a current passes though a wire in a magnetic field is formed around the wire.
- If a current carrying a wire is placed at 90 degrees to a magnetic field it feels a force.
- You can calculate the direction of the force by using the left hand rule
