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Electricity · Chapter 1: Magnetic fields

Year 11 Science · About 15 minutes with activities · Turn your sound on

Chapter 1 · Magnetic fields
An invisible field?around every magnet
Earth’s magnetic fieldevery compass lines up along it
Magnetic fielda region where forces can be detected
Steel paper clipsferromagnetic metal: feels a force
Lines go N → Soutside the magnet
Strong at the poleslines close together
Spread out: weakerfurther from the poles
Lines never cross
N facing S: attractlines run straight across the gap
N facing N: repellines bend away from each other
Neutral pointthe fields cancel
Into the pagearrow tail, going away
Out of the pagearrow tip, coming at you
Dot: out of pagefield anticlockwise
Cross: into pagefield clockwise
Further out: weakercircles spread apart
Straight insidefrom the S end to the N end
Which end is N?the current’s direction decides
Plotting compasseseach needle lines up with the field

Chapter 1 recap

  • Magnetic field: a region where magnetic forces can be detected, an area where a ferromagnetic metal or charge experiences a force. Field strength: symbol B, unit tesla (T).
  • Field lines go from N to S, are closer together where the field is stronger (at the poles), spread out further away and never cross. Unlike poles attract; like poles repel, with a neutral point between.
  • × = into the page, • = out of the page. Straight wire: concentric circles (× clockwise, • anticlockwise). Solenoid: like a bar magnet, with straight, parallel lines inside.
  • Next: Chapter 2 · Electromagnets

What turns a compass needle?

Chapter 1 · About 15 minutes · sound on

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