Chapter 9 - Magnetic Fields (unfinished) Flashcards
Learn fields for…
Single bar, repelling bars, attracting bars, solenoid
Right hand rule?d
Thumb shows direction of current, finger curling shows direction of field
How do ferrous materials work and example?
All small fields combine to make a big field
Iron
Explain why some materials have no magnetic field?
Fields produced by individual electrons cancel each other out
Fleming left hand rule?
Thumb - Thrust
First Finger - Field
Centre finger - Current Conventional
Define magnetic flux density?
The strength of a magnetic field
Define the tesla and give SI units?
The magnetic flux density is 1T when a wire carrying a current of 1A is placed at right angles to the magnetic field experience a force of 1N per metre of its length
For a uniform field, magnetic flux density?
B = F/IL
F = BIL
Draw diagram for F proportional to I experiment and 5 steps? (Or determine MFD)
1) no current in wire, scales are zeroed
2) current switches on, Ammeter used to record it
3) wire experiences upward force
4) due to N3L, equal and opposite force on magnets therefore they are pushed down on scales
5) force = mg
Torque equation?
Torque = force x separation
4 ways to increase strength of motor?
Increase current
Increase no. of coil turns
Increase length of wire in field
Increase field strength
Equation if current is not at right angles to magnetic field?
F = BILsinθ
3 points about magnetic field lines?
Go out of N and into S
Arrows show direction a free N magnet would move
Closer lines = stronger field
Factors that affect magnetic force on a moving charge? (3)
Magnetic flux density (B)
Charge on particle (Q)
Speed of particle (v)
3 equations for a magnetic force on a moving charge?
Perpendicular: F=BQv
At angle θ: F = BQvsinθ
Therefore:
F=Bev if electron is the moving charge
