Electromagnetic Forces & Induction Flashcards
How to find the direction of field lines?
Right hand rule
Thumb = Direction of current
Fingers = Direction of field
Field lines/ Current goes from?
North(out) to South(in)
Positive(out) to Negative(in)
How do you reverse magnetic field?
Reverse direction of current flow ( flip the battery)
Ways to increase strength of a magnetic field?
- Increase current
- Increase turns of coil
- Add an iron core
Flemings left hand rule
Pointer is field
Middle is Current
Thumb is Motion
When will a wire give full force?
When the wire is at 90 degrees to the magnetic field
What is an emf?
Electromotive force
What is electromagnetic induction?
Process of generating electricity from motion
How to increase electromotive force in a coil/wire
1 use stronger magnet
2 move the coil quickly relative to the magnet
3 use a coil with more turns of wire
Factors that affect size and direction of emf
1 No cutting of field lines when magnet is still
2 Wire and magnet are far, fewer field lines cut
3 Magnet moved quickly, More field lines cut => bigger emf
4 Coil effect > wire effect
A.C AND D.C generator?
Alternating current (2 rings)
Direct current ( 1 split ring)
Increase voltage in an A.C generator?
(increase rate at which field lines are cut)
1 Turn coil faster
2 Use a coil with more turns of wire
3 Use coil with bigger area
4 Use stronger magnets
Lenz’s law?
Direction of induced current always opposes change in circuit
Why use high voltages
High voltage = low temp
Low voltage = high temp => fires etc
What are transformers?
Changes voltage of an a.c supply
