Magnetism Flashcards

To revise magnetism (paper 2)

You may prefer our related Brainscape-certified flashcards:
1
Q

What will two north poles do to each other?

A

Repel

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2
Q

What will two south poles do to each other?

A

Repel

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3
Q

What will a south and north pole do to each other?

A

Attract

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4
Q

Is mangentism an example of a contact or non contact force?

A

Non contact

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5
Q

State some differences between permanent and induced magnets

A

A permanent magnet always has a magnetic field. An induced magnet only becomes magnetic when placed in a magnetic field.
Induced magnets always causes force of attraction.
Permanent magnets can attract or repel

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6
Q

State the magnetic materials

A

Iron, steel, cobalt, nickel

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7
Q

What do we call the region around a magnet where a force acts on another magnetic material?

A

Magnetic field

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8
Q

What is the relationship between the size of attraction/repulsion and distance from a magnet

A

As distance increase the force or field gets weaker

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9
Q

Where is the strength of a magnetic field the strongest?

A

The poles of a magnet

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10
Q

Why do magnetic field lines always need arrows on them?

A

The direction of the magnetic field at any point is given by the direction of the force that would act on another north pole placed
at that point. The direction of a magnetic field line is from the north (seeking) pole of a magnet to the south(seeking) pole of the magnet.

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11
Q

Describe how a magnetic compass works

A

A magnetic compass contains a small bar magnet. The Earth has a magnetic field. The compass needle points in the direction of the Earth’s magnetic field.

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12
Q

Describe how a magnetic compass can be used to find the pattern around a bar magnet.

A

Put the magnet in the middle of the piece of paper and draw around it.
Draw nine dots around the north end of the magnet.
Put a plotting compass on the paper so that its tail is over one of the dots.
Draw a dot on the paper near to the point of the compass.
Join the two dots and mark the line with an arrow.
Then move the compass so that its tail is over your new dot.
Make another dot next to the point.
Repeat until you come to the edge of the paper or loop back round to the south pole.

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13
Q

When a current flows what is always created?

A

A magnetic field

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14
Q

What factors affect the strength of the magnetic field produced by a current?

A
  1. Size of the current

2. Distance from the wire

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15
Q

What is a solenoid?

A

When a current carrying wire is turned into a coil. this will increase the strength of the magnetic field.

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16
Q

Describe the magnetic field inside a solenoid

A

The magnetic field inside a solenoid is strong and uniform.

17
Q

Describe the magnetic field around a solenoid

A

The magnetic field around a solenoid has a similar shape to that of a bar magnet.

18
Q

How can a solenoid be turned into an electromagnet?

A

Adding an iron core, this again increases the strength of the magnetic field.

19
Q

Describe the magnetic field of an electromagnet

A

Its the same as a bar magnet

20
Q

How can the strength of an electromagnet be increased?

A

Larger current
More turns
Using an iron core

21
Q

Describe the magnetic field produced by a straight wire carrying a current

A

circular rings around the wire. the right hand rule shows the direction of the magnetic field

22
Q

Describe the right hand rule for a straight wire carrying a current

A

Thumb points in the direction of the current, fingers curl around in the direction of the magnetic field

23
Q

What is the motor effect?

A

When a conductor carrying a current is placed in a permanet magnetic field the magnet producing the field and the conductor exert a force on each other.

24
Q

Describe Fleming’s left hand rule.

A

Thumb, first finger and second finger are put at right angles to each other.
Thumb - direction of force/motion
First Finger - direction of magnetic field (always from North to south)
seCond finger - direction of current (always from positive to negative)

25
Q

In the motor effect how can the size of the force be increased?

A

Larger current
Stronger permanent magnets
Longer length of wire inside the magnetic field
Keeping the conductor at a right angle to the magnetic field

26
Q

In the motor effect how can the direction of the force be reversed?

A

Reversing the direction of the current

Reversing the poles of the permanent magnets

27
Q

State the units for magnetic flux density.

A

Tesla (T)

28
Q

Describe how a coil of wire inside a magnetic field can cause rotation eg an electric motor

A

The current goes into the coil of wire, creating an electromagnetic field. This interacts with a the permanent magnetic field causing a force of attraction or repulsion.
the current then comes out of the coil changing direction so the force changes direction. This causes rotation.

29
Q

How do loudspeakers/headphones use the motor effect to create sound waves.

A

A coil of wire is wrapped around a permanent magnet. An alternating current passes through the wire creating an electromagnetic field. the magnetic field from the current and permanent magnetic interact causing a force of attraction or repulsion. As the current is a.c. the force changes between attraction and repulsion. This causes the loud speaker cone to vibrate which creates sound waves.