GCSE-Electromagnetism Flashcards

1
Q

Fleming’s left hand rule predicts the direction of the force on an electric current flowing in a …?

A

magnetic field

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2
Q

In Fleming’s left hand rule the current, field lines and force are all …?… to each other

A

perpendicular

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3
Q

In Fleming’s left hand rule the first finger represents the direction of the …?

A

magnetic field

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4
Q

In Fleming’s left hand rule the second finger represents the direction of the …?

A

current

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5
Q

In Fleming’s left hand rule the thumb represents the direction of the …?

A

force

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6
Q

Turns-ratio equation for a transformer

A

Vs/Vp = ns/np

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7
Q

Power equation for a transformer

A

VpIp = VsIs

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8
Q

The magnetic field produced by a current flowing through a coil of wire has the same shape as the field caused by a …?… …?…

A

bar magnet

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9
Q

If the current flow in a coil is clockwise as seen from one end of the coil, then that end is a …?… pole

A

South

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10
Q

If the number of turns on a current-carrying coil is increased, then the strength of its magnetic field …?

A

increases

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11
Q

If the current flowing through a coil is decreased, then the strength of its magnetic field …?

A

decreases

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12
Q

The strength of the magnetic field caused by a current-carrying coil will increase if it is given a core made of …?

A

iron

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13
Q

If a conductor and/or magnet is moved so that the conductor cuts across magnetic field lines, then …?… …?… is induced in the conductor

A

electric current

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14
Q

If the current flowing through a coil is changed, then electric current is …?… in a nearby second coil.

A

induced

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15
Q

Step-up and step-down transformers help to …?… power losses in power lines.

A

reduce

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16
Q

Equation for the force F on a straight conductor of length L carrying a steady current I at right angles to a magnetic field of strength B

A

F = BIL

17
Q

When a bar magnet is plunged into a coil, a …?… flows in the coil.

A

current

18
Q

The current induced in a coil by plunging a bar magnet into it …?… if the magnet is moved more slowly.

A

decreases

19
Q

The current induced in a coil by plunging a bar magnet into it increases if a …?… magnet is used.

A

stronger

20
Q

The current induced in a coil by plunging a bar magnet into it is…?… for a coil with fewer turns.

A

smaller

21
Q

What happens when a magnet which was plunged into a coil is then removed again at the same speed?

A

The current now induced is equal to the original but in the opposite direction.

22
Q

What happens when a bar magnet which was plunged into a coil is plunged in again at the same speed but with the opposite pole facing the coil?

A

The current now induced is equal to the original but in the opposite direction.

23
Q

The current induced in a coil by plunging a bar magnet into it stops when …?

A

the magnet is totally inside the coil.

24
Q

What happens when a magnet which was plunged into a coil sits stationary inside the coil?

A

No current is induced.

25
Q

What happens when a bar magnet is rotated close to a coil of wire?

A

An alternating current is induced in the coil.

26
Q

When the current is switched on in one coil, what happens in a nearby coil?

A

A current is induced which flows only while the first current is rising to its final steady value.

27
Q

When a steady current is switched off in one coil, what happens in a nearby coil?

A

A large current is induced in the opposite direction to that when the steady current was switched on. The induced current flows only while the first current is falling to zero.

28
Q

A coil of wire rotating between the poles of a magnet is the simplest form of …?

A

a.c. generator.

29
Q

Do transformers work with a.c. or d.c.?

A

a.c.

30
Q

What kind of transformer has more turns on the secondary coil than the primary coil?

A

Step-up transformer

31
Q

For what kind of transformer is the output voltage less than the input voltage?

A

Step-down transformer

32
Q

What does the soft-iron core in a transformer do?

A

It channels the magnetic field lines from the primary coil through the secondary coil.

33
Q

What is the difference between a.c. and d.c.?

A

d. c. is constant in size and direction.

a. c. continually changes in size and reverses in direction.