Electromagnetic Induction

https://www.youtube.com/watch?v=9gsARla8h9w

https://www.youtube.com/watch?v=AiYnDskFxTo

https://www.youtube.com/watch?v=J4L33M4-CAI

Prototype for the railgun to launch objects into outer space at 3 km/sec.

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..\..\PP movies\physics videos\MIT Physics Demo -- Inductor Radio.flv

..\..\PP movies\physics videos\Watch_This_1_25_Kilojoule_DIY_Coilgun_Smash_Various_Househol.flv

http://www.fool.com/investing/general/2015/02/08/navys-new-mach-7-cannon-could-be-a-game-changer.aspx#.VNeVwSpqB3s.email

Why does this happen?

Induction• Recall: potential difference (measured in

Volts) caused current to flow• It is also possible to induce (cause) a

current (and V) with a changing magnetic field (B)

• Relative motion between part of a circuit and a magnet is one way to induce current

Induction• Voltage, referred to as emf (electro-

motive force) often in this chapter, is also induced

• Recall: emf is defined as energy per unit charge supplied by a source of current.

• Direction of current depends on direction of B and the relative motion of the magnet & circuit (right hand rule).

Ways to induce current

1. Move circuit in/out of magnetic field, or move magnetic field across circuit

2. Rotate circuit in a constant magnetic field

3. Vary the magnetic field while the circuit is in it

• An induced current also makes its own magnetic field. The resulting induced B is always in opposition to the changing original (source) field