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Physics > Electromagnetism > Flashcards

Electromagnetism Flashcards

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1
Q

What is created around a current carrying conductor

A

A magnetic field

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2
Q

Which hand rule do we use to determine direction of a current

A

Right hand grip rule (search it up to fully learn)

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3
Q

What does a circle with a small black circle in it mean

A

Current coming out (of the page)

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4
Q

What does a circle with a cross in it mean in electromagnetism (looks like the symbol for a bulb)

A

Current going in (to the page)

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5
Q

What do the fingers mean in Flemings left hand rule, from top down if orientated with the thumb facing up (normal orientation)

A

Thumb - force
Index finger - magnetic field
Middle finger - current

FBI

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6
Q

How does a magnetic field interact around a current-carrying conductor

A

The magnetic field goes around it

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7
Q

Does the magnetic field go N-S or S-N

A

North - South

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8
Q

Do magnetic field lines ever overlap or touch

A

No

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9
Q

What is essentially an electric current

A

A moving POSITIVE charge

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10
Q

Does a moving charge experience a magnetic force

A

Yes

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11
Q

What hand rule is used for moving charges in magnetic fields

A

Flemings LH rule

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12
Q

What is Flemings LHR used for

A

Finding the direction of force, magnetic field and current for an electromagnet

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13
Q

If a charged particle moves parallel to a magnetic field, what os the effect on the trajectory of the charged particle

A

There is no magnetic force so it continues in a straight line

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14
Q

Do electrons flow in the same way or opposite to the electric current

A

Opposite

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15
Q

What direction is the force on a moving electron in a magnetic field

A

Opposite direction to a positive charge

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16
Q

What letter is used to indicate magnetic fields

A

B

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17
Q

How does a loudspeaker work

A

When the current flows through the coil in one direction, this creates a magnetic field, which interacts with the permanent magnetic field, creating a force which causes the cardboard cone to move in one direction. When the current changes direction, the cone moves in the opposite direction, creating sound waves.

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18
Q

Why do loudspeakers use a ‘varying alternating current’?

A

It must have force in both directions, so it needs to change the direction of current and the magnitude of the permanent magnetic field, which creates the force.

19
Q

What happens to the current in a loudspeaker when the sound gets louder (bigger vibrations)

A

It increases in magnitude

20
Q

What is the magnetic field around a direct current (d.c.) motor?

A

The same size and direction

21
Q

Which way does current flow

A

+ to -

22
Q

What does the split ring commutator do

A

Reverses the direction of the current every half turn of the coil

23
Q

See the split ring commutators diagram

A

Ok

24
Q

What do magnets do in relation to other magnets

A

They repel like poles and attract unlike poles

25
Q

What do magnets do to magnetic substances

A

Attract them

26
Q

What is a magnetically ‘hard’ material

A

It retains any induced magnetic properties

27
Q

What are magnetically ‘soft’ materials

A

Materials that can lose any induced magnetism

28
Q

What type of core is used in electromagnets

A

Soft iron cores

29
Q

How can you make an electromagnet stronger (4)

A
  1. Increase the current
  2. Increase the number of turns in the coil
  3. Densely pack the coil
  4. Add a soft iron core
30
Q

How is a electromagnet constructed

A

A wire is coiled around a soft iron core

31
Q

What is the right hand rule

A

Grab a single wire with your thumb aligned with the conventional current, your fingers will show you the direction of the magnetic field

32
Q

What is conventional current

A

Positive to negative

33
Q

What happens to some objects when they are placed in a magnetic field and what are these objects called

A

They can become magnetic. They are referred to as being magnetically ‘soft’

34
Q

Can magnetic field lines cross

A

No

35
Q

How do you find the magnetic field pattern for a bar magnet

A

Iron filings method - sprinkle iron filings on a piece of paper above a bar magnet, then the filings will make the lines. Then draw the lines on the paper.

Compass method - put many compasses around the magnet - the direction of the needles will show the direction of the field lines - then draw the lines

36
Q

What does an electric current going through a conductor produce

A

A magnetic field

37
Q

What is the magnetic field for a flat circular coil when carrying current

A

Circles around each side (see google)

38
Q

What is the magnetic field lines for a solenoid (coiled up wire) when carrying current

A

Passing through the coil and one on the outside on each side (see google)

39
Q

What is the magnetic field of a wire when carrying a current

A

A circle (use right hand rule for direction)

40
Q

Can magnets be charged

A

No

41
Q

What direction do magnetic field lines go

A

North to South

42
Q

What direction does convection current flow

A

+ to -

43
Q

What direction do electrons flow

A
  • to +

Physics (12 decks)

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