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physics > Magnetism/ electromagnetism > Flashcards

Magnetism/ electromagnetism Flashcards

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1
Q

any current….

A

makes a magnetic field

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2
Q

like poles…

A

repel

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3
Q

opposite poles…

A

attract

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4
Q

uniform field

A
  • same strength at all points
  • place two magnets near ( but not touching) with N facing S
  • field lines are equidistant and parallel
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5
Q

straight wire magnetic field

A

makes a circular field
right hand grip rule

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6
Q

right hand grip rule

A

thumb = current
fingers = field

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7
Q

wire cross section - cross

A

current into page away from you

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8
Q

wire cross section - dot

A

current out of page towards you

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9
Q

soft magnetic material

A

easily magnetised/ demagnetised
eg IRON

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10
Q

hard magnetic material

A

remains magnetised
eg STEEL

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11
Q

magnetic material eg

A

iron
steel
nickel
colbalt

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12
Q

field flows

A

N>S

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13
Q

current flows

A

+>-

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14
Q

how to draw field shape

A
  • place a plotting compass in the field
  • note/draw direction
  • move to new place and repeat
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15
Q

where is field strongest

A

where field lines are closest

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16
Q

how to make solenoid field stronger

A
  • more current
  • more coils/ turns in the wire
  • add an iron core
17
Q

moving charged particle in magnetic field - parallel to field

A

have no force on it

18
Q

moving charged particle in magnetic field - 90 to field

A

deflected off course

19
Q

motor effect

A
  • a current makes a magnetic field
  • if this is in another magnetic field the two INTERACT
  • this produces a FORCE
20
Q

flemmings left hand rule

A

thuMb = Movement
First finger = Field N>S
seCond finger = Current +>-
(MFC)

21
Q

motor

A

contains a coil of wire inside a magnetic field
- when a current passes into the coil it produces its own magnetic field
- this INTERACTS causing a FORCE on the wire
- since the current on each side of the wire is in OPPOSITE directions this force is too - causes it to ROTATE

22
Q

split ring commutator

A

switches the direction of the current every half turn to keep it spinning

23
Q

metal/ graphite brushes

A

feed current into the coil

24
Q

how to make force on wire stronger

A
  • increase current
  • stronger magnet
  • more wire in-between magnets
  • more turns
25
Q

how to increase speed of motor

A
  • more coils
  • larger current
  • stronger magnets
26
Q

loud speaker

A
  • coild of wire is wrapped around a paper tube attached to the cone
  • when there is ac in the coil the cone moves
27
Q

How loudspeaker produces a sound wave

A
  • direction of magnetic field is changing (AC)
  • field of coil INTERACTS with magnet field
  • produces FORCE on coil
  • direction of force changes
  • so cone VIBRATES
  • air particles are made to VIBRATE
28
Q

electromagnetic induction

A

how electricity is generated
- if magnetic field lines are CUT by a wire
- it INDUCES a voltage + current

29
Q

how to increase size of current + voltage induced

A
  • faster cutting
  • stronger magnetic field
  • more turns of coil
30
Q

generator - how ac current is induced

A
  • spin the coil inside the magnetic field
  • direction of cutting changes
  • so direction of induced current changes - ac
31
Q

generator

A

identical to a motor

physics (19 decks)

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