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Physics- I Hate You > electromagnetism > Flashcards

electromagnetism Flashcards

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1
Q

how can a magnetic field be detected

A

by its effect on another magnet or a moving charged particle

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2
Q

magnetic field line drawing

A

north on left south on right
three lines as curves from north to south on top and same on bottom
draw the lines with arrows pointing north to south

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3
Q

uniform magnetic field

A

a magnetic field of constant strength

represented by evenly spaced parallel magnetic field lines between the magnet

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4
Q

shape of a magnetic field can be revealed using

A

iron filings

plotting compass

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5
Q

plotting compass

A

shows the direction of a magnetic field

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6
Q

soft magnetic field

A

easily magnetised and demagnetised

example: iron

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7
Q

hard magnetic field

A

difficult to magnetise and demagnetise

example: steel

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8
Q

if two magnets are in close proximity to each other with two unlike poles together

A

a uniform magnetic field forms

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9
Q

only three magnetic elements at room temp

A

iron, nickel and cobalt

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10
Q

iron filling experiment

A
  • magnet
  • paper on top
  • sprinkle iron filling while tapping paper
  • iron will line up according to shape
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11
Q

plotting compass experiment

A
  • paper down
  • magnet on top
  • plotting compass close to magnet
  • where arrow points to magnet you draw a line
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12
Q

magnet field around a current carrying wire

A

when current flows, convectional current flows in a wire, it gets hot and a magnetic field appears

this happens to even non magnetic materials

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13
Q

the motor effect

A
  • when a current flows in a wire a magnetic field is produced
  • this magnetic field interacts with the magnetic field of the permanent magnet
  • the wire experiences a force and is pushed out or pulled in
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14
Q

ho can we increase the size of the force extended on the wire

A

increase the voltage
use a stronger permanent magnet
the speed of movement increases
the number of turns on the coil is increased

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15
Q

how can we change the direction of motion

A

reverse the direction of the current flow

reverse the direction of the magnetic field

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16
Q

alloys

A

mixture of two or more metals

17
Q

destorying magnets

A

dropping them (vibrates)
heat it up (particles vibrate)
a coil with the alternating current can demagnetise it

18
Q

the loudspeaker

A

an ac current is needed for the speaker to function, this will flow through the coil

which produces a magnetic field around the coil that is constantly changing. This will interact with the field of the permanent magnet.

19
Q

an electric motor

A

changes electrical energy into kinetic energy/rotational energy/mechanical energy

describe the motor effect and then say, this causes it to rotate

used for things like hairdryers, fans, cars, planes, fridges, microwaves

20
Q

what is needed to keep the coil rotating in an electric motor

A

a split ring communicator

21
Q

to increase the magnitude of an induced current

A
  • increase the rate at which the magnetic field changes

increase the strength of the permament magnet

22
Q

dynamo

A

small generator fitted to a bike to provide electricity for ht lights

inside, a permament magnet is rotated in the middle of the coils of wire this produces a magnetic field. this produces a voltage which causes current to flow (ac)

23
Q

rotating magnet vs coil

A

split ring not needed

24
Q

lemmings left hand rule

A

thumb- force
first finger- field (North to south)
second finger- (current positive to negative)

25
Q

devices which use the changing electromagnetic force on a coil of fire in a magnetic field to make a cone vibrate

A

loudspeaker, headphones

26
Q

sometimes a wire carries a current in a magnetic field but no electromagnetic force acts on it explain why

A

if the wire/current is parallel to the magnetic field

27
Q

what is shown by the direction of the arrow in a magnetic field line

A

the direction in which a free north pole would point

28
Q

name one application of the effect indicated by the left hand rule

A

motor

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