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Physics > Magnetism > Flashcards

Magnetism Flashcards

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1
Q

Magnetism and magnetic materials

A

Magnets attract to objects containing iron, steel, nickel

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2
Q

Magnetically hard

A

Hard to demagnetise, will retain magnetism once other magnet is removed
Steel

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3
Q

Magnetically soft

A

Easy to magnetise and demagnetise but will lose magnetic ability when other magnet removed

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4
Q

Magnetic fields

A

Symmetrical
Field lines close together at poles
No crossover
Hairy hamburger

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5
Q

How to find magnetic field lines

A

Use plotting compass
Place compass on the end of one pole and put a dot where the tail of the needle is
Place compass tail on dot and put another dot on where the other side of the tail is
Repeat
Join lines together in a curve
N=>S

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6
Q

Laws of magnetism

A

Similar poles repel
Opposite poles attract
Uniform magnetic field between poles

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7
Q

How to make a magnet

A

Atom, tiny magnet called dipole
Many dipoles, domain
If unaligned, domains cancel out
If domains line up, magnetic

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8
Q

Electromagnetism

A

Magnetic field will be established around current carrying wire
Circular magnetic field

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9
Q

Right hand grip rule

A

Thumb, current
Fingers, field direction
Dart needle, towards
Tail away

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10
Q

Magnetic field around a solenoid

A

Solenoid has north and South Pole

Like a bar magnet

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11
Q

Solenoid can be strengthened by

A

More coils
Iron core
More current

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12
Q

Uses of electromagnetism

A

Relays, small voltage used to switch a larger cola tape appliance on
Circuit breakers, circuit broken if excess current flows caused by malfunction
Electric bell
Loudspeaker, uses AC and permanent magnet to cause movement

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13
Q

The motor effects

A

When 2 field lines cross, wire experiences a force when in a magnetic field
FLHR
Force on charged particle when it moves in a magnetic field as long as the motion is not parallel to the field

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14
Q

FLHR

A

Thumb, motion
First finger, field
Second finger, current

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15
Q

How to change the direction of induced force

A

Flip the battery

Flip the magnet

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16
Q

How to increase the force induced

A

Add more current
Increase magnetic field strength
Increase no of wires

17
Q

Generators

A

Convert mechanical energy into elec energy

18
Q

DC motor

A 
Converts electrical energy and magnetism into movement
N=>S
Coil rotates, cuts through field lines
Induces current in coil
1 terminal, always +
1 terminal, always -
Direction of current does not change
Split rings rotate with coil
19
Q

Increase motor strength

A

More coils on rotating part
Increase current flow
Increase magnetic strength
Increase area of coil

20
Q

Electromagnetic induction

A

Is a wire is moved through a magnetic field, a current is produced
Induction also occurs if a magnet is moved in a coil of wire or if a coil of wire rotates in a magnetic field
KE=>electrical
Faster movement, higher pd generated

21
Q

FRHR

A

Thumb, motion
First finger, magnetic field
Second finger, current

22
Q

How would movement of magnet affect galvanometer

A

More KE=>more elec energy, galvanometer will show more current
Change direction, change direction of current
More coils, more induction of current
Stronger magnet, greater induced current
No movement, no change on galvanometer

23
Q

AC generator

A

Magnetic field from N=>S
Cutting through magnetic field lines as coil rotates which induces a current in coil
FRHR shows that current is in diagram
One slip ring, +
Other slip ring,-
Half a cycle later, coil in field has rotated 180, reverses current in circuit

24
Q

How to increase voltage in generators

A

Spin it faster
Stronger magnet
Larger number of coils
Larger area of coils

25
Q

Transformers

A

Transforms AC voltage to a different value
Step up and step down
AC produced a continually changing magnetic field within the iron core, Magnetic field indices a voltage in the secondary coil which induces a current

26
Q

Energy waste from transformers

A

Heat wasted, current flows through
Magnetic field in core produces eddy currents, cause heating
Iron core, laminated to reduce eddy currents
Magnetic field may leak out of core if there is a gap between the p and s

27
Q

What happens when transformation happens

A

Voltage stepped up, after it has left the power station, vvvvv low current
Voltage stepped down as sub stations, current increases

28
Q

The National Grid

A

Boiler, turbine, generator, transformer
Low current, less power loss through heating
P=I^2R

Physics (11 decks)

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