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MAC short physics facts > Magnetism > Flashcards

Magnetism Flashcards

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1
Q

Laws of magnetism

A

Like poles repel
Unlike poles attract

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2
Q

What are the names of the 2 magnetic poles?

A

North
South

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3
Q

What are the only 3 elements that can be magnetised?

A

iron
cobalt
nickel

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4
Q

What magnetic element is steel an alloy of?

A

iron

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5
Q

What is a magnetic field line?

A

Shows the force in a magnetic field on another magnet
Field lines run north to south
Field lines never cross

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6
Q

Expt to show the pattern of a magnetic field around a permanent bar magnet?

A

Lay paper over the magnet/s
Spinkle iron filings
Tap the paper

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7
Q

Expt to show the direction of the magnetic field lines around a permanent bar magnet?

A

Place plotting compasses around the magnet/s
Draw on the paper below the direction of the needle
Join up the small arrows to get the magnetic field lines

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8
Q

Describe the pattern of the magnetic field around two magnets with N and S poles facing each other

A

Uniform field between N and S poles
Beetle shape around both magnets

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9
Q

Describe the pattern of the magnetic field around two magnets with N and N poles facing each other

A

Beetle shape around each magnet
Neutral point between N and N pole as the repel

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10
Q

Describe the magnetic field around a bar magnet

A

Beetle shape
Field lines run N to S
Field lines never cross

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11
Q

What is a magnetically hard material?

A

One that keeps retains its magnetism
eg steel

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12
Q

What is a magnetically soft material?

A

One that gains and looses magnetism easily
eg soft iron

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13
Q

How do you create a uniform magnetic field using 2 bar magnets?

A

Place magnets N facing S close to each other. Field in between in uniform

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14
Q

Shape of a mag field around a wire carrying a current and how to we determine its direction?

A

Circular
Use right hand grip rule

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15
Q

Construction of an electromagnet?

A

coil of wire
around a soft iron core
dc current supply

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16
Q

Shape of filed around a solenoid

A

same as a bar magnet

17
Q

Shape of field around a flat coil

A

use right hand grip rule to work it out

18
Q

Why is a force exerted on a current carrying wire sitting at right angles in a magnetic field?

A

Mag field of wire with current interacts with mag field of magnets to produce motion

Magnetism + current = motion

19
Q

Does a charged particle moving at right angles in a magnetic field experience a force on it ?

A

Yes - as a charged particle is a tiny bit of current!

20
Q

What is the motor effect and what hand rule do we use to determine direction of the movement?

A

Magnetism + current = motion
Fleming’s Left hand rule

21
Q

How do you increase the size of the force in the motor effect?

A

Larger current
Stronger magnets
Coil more wire - more coils

22
Q

What is electromagnetic induction and how do we determine the direction of induced voltage?

A

Magnetism + motion = current (induced voltage)
all at right angles
Fleming’s right and rule

23
Q

Factors affecting the size of the induced voltage?

A

Stronger magnets
Faster movement
More coils

24
Q

Motor effect or electromagnetic induction:

The loudspeaker?

A

motor effect

25
Q

Motor effect or electromagnetic induction:

The motor?

A

motor effect

26
Q

Motor effect or electromagnetic induction:

The generator?

A

electromagnetic induction

27
Q

Motor effect or electromagnetic induction:

The microphone?

A

electromagnetic induction

28
Q

Motor effect or electromagnetic induction:

The transformer?

A

electromagnetic induction

29
Q

What does a step up transformer do?

A

steps up voltage

30
Q

What does a step down transformer do?

A

steps down voltage

31
Q

Why do we transmit electricity on the national grid at very high voltage?

A

High voltage means less energy lost as heat in wire as:
Power loss = I 2 R

32
Q

For a 100% efficient transformer…..

A

Power in = power out
IV primary = IV secondary

33
Q

Transformer turns equations:

A

primary V = primary turns
secondary V secondary turns

34
Q

Describe stages of how a transformer works:

A

AC current passed through primary coil
Primary magnetic field grows
Soft iron core channels this changing mag field into secondary coil
Secondary coil cuts changing magnetic field
produces an induced voltage in secondary coil

35
Q

What has to be happening for an induced voltage is produced?

A

The wire or coil must be cutting a magnetic field

MAC short physics facts (10 decks)

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