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Gcse Physics > TOPIC 7 FINAL > Flashcards

TOPIC 7 FINAL Flashcards

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1
Q

A magnetic has what?

A

A north and south pole.

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2
Q

What do all magnets produce?

A

A magnetic field

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3
Q

When two like poles meet what happens?

A

A force of repulsion

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4
Q

When two opposite poles meet what happens?

A

A force of attraction

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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 and only experience a force of attraction and repulsion.

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15
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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16
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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17
Q

Name the 4 magnetic materials

A

Iron
Steel
Cobalt
Nickel

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18
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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19
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

20
Q

What does the strength of the magnetic field through a wire depend on?

A

Size of the current. A larger current produces a larger magnetic field.

21
Q

Where else is the magnetic field strongest at in a current carrying wire?

A

It is strongest closer to the wire, as we move further away from wire, the strength of magnetic field decreases.

22
Q

if we change the direction of the current in a current carrying wire in a closed circuit what does this mean?

A

We change the direction of the magnetic field.

23
Q

How do we work out the direction of the magnetic field produced by a wire?

A

We use the right hand grip rule. Using your right hand, point your thumb in the direction of current and curl your fingers. The direction of your fingers is the direction of the field.

24
Q

What is a final way to increase the strength of the magnetic field that a wire produces.

A

Wrapping wire into a coil called a solenoid.

25
Q

What happens when we use a solenoid in a current carrying wire?

A

When we turn on current we get a strong and uniform magnetic field, inside the solenoid.

26
Q

What is similar about the magnetic field of a bar magnet and the magnetic field around solenoid?

A

It has the same magnetic field around it.

27
Q

What can you use to work out what end is north pole and what end is south pole of a solenoid?

A

By using the right hand grip rule.

28
Q

What are the 3 ways to increase the magnetic field produced by a solenoid?

A

1) Increase the current, strengthening the magnetic field
2) Increase the number of coils to increase magnetic field.
3) Place an iron core inside the solenoid increasing the strength of the magnetic field.

29
Q

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

A

Because it is an induced magnet when current is flowing.

30
Q

What is a Electromagnet?

A

A solenoid containing a iron core.

31
Q

What makes Electromagnets useful?

A

We can turn on and off the electromagnet and also we can change the strength of the magnetic field.

32
Q

What is Direct current?

A

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

33
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.

34
Q

How do you calculate size of force acting on a conductor in a magnetic field?

A

Force (N) = B (magnetic flux density, Tesla) X I (current Amps) X L (length of conductor in M)

35
Q

What does the question only apply to?

A

It only applies to a wire which is at right angles to the magnetic field. It will not experience a force at all if in parallel.

36
Q

What are the 3 factors that affect size of the force?

A

1) The magnetic flux density
2) Current
3) Length of conductor

37
Q

A 35 cm long piece of wire is at 90% to the external magnetic field. The wire experiences a force of 9.8 N when a current of 5.0 A is flowing through it. Calculate the magnetic flux density of the field?

A

35 cm = 0.35m
b = F /I X L
9.8 / (5.0 X 0.35)
= 5.6T

38
Q

What can you use to find the direction of the force?

A

Fleming’s left hand rule.

39
Q

How do you use Fleming’s left hand rule?

A

1) Place first finger in the direction of the magnetic field. (N to S)
2) Now point your second finger in the direction of the current (+ to -)
3) The direction that your thumb is pointing, shows you the direction of the force.

40
Q

What is a useful application of the Motor effect?

A

Electric motors

41
Q

What can you use to find the direction of the force in an electric motor?

A

Using Fleming’s left hand rule.

42
Q

What is the problem of Electric motors?

A

The loop rotates at 90’, this is a problem as once the loop is at 90’, it will stop rotating.

43
Q

What is a split ring commutator?

A

It is a clever way of swapping the contacts every half turn to keep the motor from rotating in the same direction.

44
Q

How can the direction of the electric motor be reversed?

A

1) Swapping the polarity of the dc supply ( reversing the current)
2) Swapping the magnetic poles over (reversing the field)

45
Q

What are the 3 ways to increase the speed of the electric motor be increased?

A

1) Increasing the current
2) Adding more turns to the coil
3) increasing the magnetic flux density

Gcse Physics (9 decks)

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