Achieve an A* in your A Level Physics exams with our expertly written notes on 'Magnetic Fields'. Created by a student who scored an A*, these notes are clear and easy to understand. Explore the principles of magnetic fields, covering topics such as magnetic flux, electromagnetism, and the behavior...
3.7.5.1.
Magnetic field line def.?
- the line in a magnetic field along which a north pole would move
Magnetic field of the Earth?
- top of the globe/north pole = magnetic south
- bottom of the globe/south pole = magnetic north
==> field lines point from bottom of globe to top
Direction of magnetic field around a current-carrying wire?
- right hand grip rule
Equation for Flemming's LHR (aka for the force experience by a current carrying wire
in a magnetic field)?
- F = BIl
- where l is length of wire INSIDE the magnetic field
- B is magnetic flux density in Teslas
- I is current
Assumption of F = BIl equation?
- so the OG full equation is F = BIlsinTheta
--> where Theta = angle between wire and magnetic field lines
--> when the wire is at right angles to the magnetic field --> sinTheta = sin90 = 1
==> SO BIlsinTheta becomes F = BIl
==> we assume the wire is at right angles to the magnetic field
When is the force in a current carrying wire in a magnetic field the greatest?
- when the wire is at right angles to the field
When is the force in a current carrying wire in a magnetic field 0?
- when the fire is parallel to the field
,Descr. how an electric motor works?
~its components~
- a coil of insulated wire
- U- shaped magnet with north and south poles
~its mechanism~
1) DC current is supplied to the coil via a split-ring commutator
2) the direction of the current is reversed by the split ring commutator every half rotation (180
degrees)
==> current reverses direction when it moves from one of the poles to the next
==> the force on each side has a consistent same direction that it turns the coil in
3) due to Flemming's LHR opposite forces direction wise) act on opposite sides of the wire
==> these forces make the coil spin
Calc. the torque in the motor effect?
, https://www.youtube.com/watch?v=uFB-I3bSvDA
3.7.5.2.
Descr. what happens to charged particles in a magnetic field?
- they get deflected
bcs..watch from 13.30: https://youtu.be/RjY5bZ4Bl8o?feature=shared
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