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Gcse Physics > Topic 7 > Flashcards

Topic 7 Flashcards

1
Q

What do all magnets produce?

A

A magnetic field

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2
Q

When two poles of a magnet are put near each other what do they exert?

A

A force

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3
Q

When two like poles meet what happens?

A

They repel from each other

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4
Q

When two opposite poles meet what happens?

A

They attract to each other

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5
Q

Magnetic forces are always what?

A

A non-contact force.

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6
Q

What is a Magnetic field?

A

An area around an object where it experiences a magnetic force.

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7
Q

What can you use to show the direction of a Magnetic field?

A

A compass

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8
Q

What is in a Compass?

A

A tiny bar magnet

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9
Q

In a compass the North pole is always attracted to what?

A

The south pole, so the compass points in the direction of the magnetic field.

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10
Q

How do you know in a magnetic field where it is strongest?

A

Where the lines are close together near the poles of the bar magnet.

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11
Q

Where is the magnetic field weakest at?

A

When the lines are not close together.

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12
Q

The earth has what?

A

A magnetic field

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13
Q

On a compass where would north point to on the earth’s magnetic field?

A

It will point to earth’s magnetic south

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14
Q

What is a Permanent Magnet?

A

They produce their own magnetic field.

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15
Q

If the magnet is Permanent what does that also mean?

A

Then it can be both Attracted and repelled to.

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16
Q

What is an Induced Magnet?

A

Are magnetic materials that turn into a magnets when they are placed in a magnetic field.

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17
Q

If a magnet is induced what does it mean?

A

It will only ever be Attracted to a permanent magnet.

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18
Q

Name the 4 magnetic materials

A

Iron
Steel
Cobalt
Nickel

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19
Q

In a Series circuit if the switch is open what does it mean?

A

Their is no current which means their is no magnetic field around the wire

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20
Q

In a Series circuit if Switch is closed what does that mean?

A

It means Direct current can flow producing a magnetic field around the whole wire

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21
Q

If we take a wire and pass it through a electrocurrent what does it produce?

A

A magnetic field

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22
Q

If we change the direction of the current what else changes?

A

The direction of the magnetic field.

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23
Q

What can you use to work out the magnetic field direction?

A

The right hand grip rule

24
Q

How do you use the right hand grip rule?

A

Use your right hand and point finger in the direction of the current and curl your fingers
The direction that your fingers curl tell you the direction of the magnetic field.

25
Q

What does the strength of the magnetic field changes with?

A

The current and the distance from the wire

The larger the current through the wire, the stronger the current is.

26
Q

What is a Solenoid?

A

A coil of wire

27
Q

How can you increase the strength of the magnetic field through a wire?

A

By wrapping more coils around the wire this is called a solenoid.

28
Q

Describe how the magnetic field is inside a solenoid?

A

It is strong and uniform( it has the same strength and direction at every point in that region)

29
Q

Describe the magnetic field outside the solenoid?

A

Its just like a bar magnet

30
Q

Because the magnetic field of a solenoid outside is just like a bar magnet what does it mean it must have?

A

At the ends of the solenoid it acts like it has a north and south pole just like a bar magnet.

31
Q

How can you work out which end of the solenoid is the north and south pole?

A

Using the right hand grip rule

32
Q

How can you increase the magnetic field strength even more in a solenoid?

A

By placing a iron rod in the center of the rods?

33
Q

Why would you place an iron rod in the center of the solenoid?

A

Because it is an induced magnet when current is flowing.

34
Q

What is an Electromagnet?

A

A solenoid containing a iron core which the electromagnet can be switched on and off

35
Q

What is Direct current?

A

In a circuit the current from the cell only moves in one direction

36
Q

What is Alternating current?

A

Mains electricity is Alternating current where the currents changes direction

37
Q

Name an example of an Electromagnet?

A

Loud Speaker

38
Q

How does a Loud speaker work?

A

1) As a current passes through the coil of wire it generates a magnetic field becoming an electromagnet
2) The magnetic field from the coil now interacts with the magnetic field from the permanent magnet, the magnetic field either attracts or repels.
3) This produces a resultant force which causes the cone to move, when the direction of the current changes, the direction of the forces changes to the opposite direction.
4) The changing direction of the electromagnetic field and the force is generated causes the cone to move in and out generating sound waves

39
Q

What is the Motor effect?

A

When a current carrying a wire will experience a force when placed in a Magnetic field because the Magnetic field interacts with magnetic field of the magnet.

40
Q

How can you increase size of force?

A

By increasing the strength of the magnetic field or by increasing the size of current.

41
Q

What do you use to find direction of a force?

A

Fleming’s left hand rule.

42
Q

How do you use Fleming’s left hand rule.

A

1) Place first finger in the Direction of Magnetic field (N to S)
2) Then place second finger in the direction of current (+ to -)
3) Finally the direction of your thumb shows the direction of the force.

43
Q

What happens when the current carrying wire is parallel to the magnetic field?

A

It will not exert a force

44
Q

What is the only way a current carrying can exert a force on a wire?

A

The wire has to be at 90 degrees to the magnetic field.

45
Q

How can you find the size of the force?

A

Using F=Bil

46
Q

What is the F in the F=Bil equation?

A

Force (N)

47
Q

What is the B in the F=Bil equation?

A

Magnetic flux destiny (magnetic field, T)

48
Q

What is the I in the F=Bil equation?

A

Current in (A)

49
Q

What is the L in the F=Bil equation?

A

Length of the conductor in (M)

50
Q

One useful application of the motor effect is what?

A

Electric motors

51
Q

If we place a loop of wire carrying current into a magnetic field what will happen?

A

The currents runs in opposite directions

52
Q

On the left hand side of a the loop of wire what is the direction of the force?

A

Upwards(using Fleming’s left hand rule)

53
Q

On the right hand side of a the loop of wire what is the direction of the force?

A

Downwards(using Fleming’s left hand rule)

54
Q

Because the forces act up and down what happens to the wire?

A

it rotates in a clockwise direction

55
Q

What are the 2 ways you can reverse the direction of rotation of a motor?

A

Reversing the direction of the magnetic field (swapping poles)
Swapping the polarity of the dc supply( reversing current direction?

56
Q

What does a split-ring commutator do?

A

It is a clever way of reversing the current direction every half turn because otherwise it would stop

Gcse Physics (9 decks)

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