What is electromagnetic induction ?

Electromagnetic induction is the effect of inducing e.m.f. in a conductor due to the relative motion between a conductor and a magnetic field .

How can a voltage be induced in a wire?

A voltage can be induced in a wire by moving it through a magnetic field.

True or False? A voltage can only be induced by moving a conductor in a magnetic field.

False. A voltage can also be induced by placing a stationary conductor in a changing magnetic field.

How can the direction of an induced voltage be reversed ?

The direction of an induced e.m.f. can be reversed by: Reversing the direction of motion (of the magnet or conductor) Swapping the poles of the magnet

True or False? When the north pole of a bar magnet is pushed towards a coil, the end of the coil begins to act as a south pole.

False. When the north pole of a bar magnet is pushed towards a coil, the end of the coil begins to act as a north pole. As a result, the two like poles repel in order to oppose the motion of the magnet.

What is an A.C. generator ?

An A.C. generator is a device which converts energy from a mechanical store to an electrical store.

What is the output of an A.C. generator?

The output of an A.C. generator is alternating current .

What components make up a simple A.C. generator?

A simple A.C. generator consists of: A rectangular coil of wire rotating in a magnetic field Slip rings and brushes

What is the purpose of the slip rings ?

The purpose of slip rings is to provide a connection between the rotating coil and the external circuit.

How often does the direction of the current reverse as an A.C. generator rotates?

The direction of the current reverses every half rotation of the coil in the A.C. generator.

True or False? A maximum value of current is induced when the coil is parallel to the magnetic field.

False. A maximum value of current is induced when the coil is perpendicular to the magnetic field.

True or False? There is a point in the rotation of the coil where no current is induced.

True. No current is induced when the coil is parallel to the field.

What is the shape of the graph of output current against time for an A.C. generator?

For an A.C. generator, the shape of the graph of output current against time is a sine or cosine curve .

What is the frequency of an A.C. output?

The frequency of an A.C. output is the number of complete cycles it makes each second e.g. 1 cycle per second = 1 Hz.

How can the size of the induced current be increased in an A.C. generator?

In an A.C. generator, the size of the induced current can be increased by: adding more turns to the coil rotating the coil faster increasing the strength of the magnet

What is the function of a transformer?

The function of a transformer is to change the value of an alternating potential difference or current .

Describe the structure of a simple transformer.

A simple transformer consists of: a soft iron core a primary coil a secondary coil

Which type of transformer increases the potential difference of a power source?

A step-up transformer increases the potential difference of a power source.

Which type of transformer decreases the potential difference of a power source?

A step-down transformer decreases the potential difference of a power source.

True or False? When an alternating current is supplied to the primary coil of a transformer, it produces a changing magnetic field in the iron core.

True. When an alternating current is supplied to the primary coil of a transformer, it produces a changing magnetic field in the iron core.

True or False? A step-down transformer has fewer turns on the primary coil than the secondary coil.

False. A step-down transformer has fewer turns on the secondary coil than the primary coil.

True or False? When a changing magnetic field is produced in the iron core of a transformer, it induces a changing potential difference in the secondary coil.

True. When a changing magnetic field is produced in the iron core of a transformer, it induces a changing potential difference in the secondary coil.

Which type of transformer has more turns on the primary coil than the secondary coil?

A step-down transformer has fewer turns on the primary coil than the secondary coil.

Which type of transformer has fewer turns on the primary coil than the secondary coil?

A step-up transformer has fewer turns on the primary coil than the secondary coil.

True or False? To increase potential difference, a transformer must have more turns on the secondary coil than on the primary coil.

True. To increase potential difference, a step-up transformer must have more turns on the secondary coil than on the primary coil.

What is the purpose of transformer calculations?

The purpose of transformer calculations is to determine the output potential difference (voltage) of a transformer based on: Number of turns on the primary and secondary coils Input potential difference (voltage)

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What is electromagnetic induction?
Electromagnetic induction is the effect of inducing e.m.f. in a conductor due to the relative motion between a conductor and a magnetic field.
How can a voltage be induced in a wire?
A voltage can be induced in a wire by moving it through a magnetic field.
True or False?
A voltage can only be induced by moving a conductor in a magnetic field.
False.
A voltage can also be induced by placing a stationary conductor in a changing magnetic field.
How can the direction of an induced voltage be reversed?
The direction of an induced e.m.f. can be reversed by:
- Reversing the direction of motion (of the magnet or conductor)
- Swapping the poles of the magnet
True or False?
When the north pole of a bar magnet is pushed towards a coil, the end of the coil begins to act as a south pole.
False.
When the north pole of a bar magnet is pushed towards a coil, the end of the coil begins to act as a north pole.
As a result, the two like poles repel in order to oppose the motion of the magnet.
State the factors that will affect the size of the induced potential difference in the wire in the diagram.
The size of the induced potential difference in the wire in the diagram is determined by:
- The speed at which the wire is moved
- The strength of the magnetic field
State the factors that will affect the size of the induced potential difference in the coil in the diagram.
The size of the induced potential difference in the coil in the diagram is determined by:
- The speed at which the magnet is moved
- The strength of the magnetic field
- The number of turns on the coils of wire
- The size of the coils
- The strength of the magnetic field
What is an A.C. generator?
An A.C. generator is a device which converts energy from a mechanical store to an electrical store.
What is the output of an A.C. generator?
The output of an A.C. generator is alternating current.
What components make up a simple A.C. generator?
A simple A.C. generator consists of:
1. A rectangular coil of wire rotating in a magnetic field
2. Slip rings and brushes
What is the purpose of the slip rings?
The purpose of slip rings is to provide a connection between the rotating coil and the external circuit.
How often does the direction of the current reverse as an A.C. generator rotates?
The direction of the current reverses every half rotation of the coil in the A.C. generator.
True or False?
A maximum value of current is induced when the coil is parallel to the magnetic field.
False.
A maximum value of current is induced when the coil is perpendicular to the magnetic field.
True or False?
There is a point in the rotation of the coil where no current is induced.
True.
No current is induced when the coil is parallel to the field.
What is the shape of the graph of output current against time for an A.C. generator?
For an A.C. generator, the shape of the graph of output current against time is a sine or cosine curve.
What is the frequency of an A.C. output?
The frequency of an A.C. output is the number of complete cycles it makes each second e.g. 1 cycle per second = 1 Hz.
How can the size of the induced current be increased in an A.C. generator?
In an A.C. generator, the size of the induced current can be increased by:
- adding more turns to the coil
- rotating the coil faster
- increasing the strength of the magnet
What is the function of a transformer?
The function of a transformer is to change the value of an alternating potential difference or current.
Describe the structure of a simple transformer.
A simple transformer consists of:
- a soft iron core
- a primary coil
- a secondary coil
Which type of transformer increases the potential difference of a power source?
A step-up transformer increases the potential difference of a power source.
Which type of transformer decreases the potential difference of a power source?
A step-down transformer decreases the potential difference of a power source.
True or False?
When an alternating current is supplied to the primary coil of a transformer, it produces a changing magnetic field in the iron core.
True.
When an alternating current is supplied to the primary coil of a transformer, it produces a changing magnetic field in the iron core.
True or False?
A step-down transformer has fewer turns on the primary coil than the secondary coil.
False.
A step-down transformer has fewer turns on the secondary coil than the primary coil.
True or False?
When a changing magnetic field is produced in the iron core of a transformer, it induces a changing potential difference in the secondary coil.
True.
When a changing magnetic field is produced in the iron core of a transformer, it induces a changing potential difference in the secondary coil.
Which type of transformer has more turns on the primary coil than the secondary coil?
A step-down transformer has fewer turns on the primary coil than the secondary coil.
Which type of transformer has fewer turns on the primary coil than the secondary coil?
A step-up transformer has fewer turns on the primary coil than the secondary coil.
True or False?
To increase potential difference, a transformer must have more turns on the secondary coil than on the primary coil.
True.
To increase potential difference, a step-up transformer must have more turns on the secondary coil than on the primary coil.
State the type of transformer in the diagram.
The type of transformer in the diagram is a step-down transformer.
State the primary voltage of the transformer in the diagram.
The primary voltage of the transformer in the diagram is 300 V.
What is the purpose of transformer calculations?
The purpose of transformer calculations is to determine the output potential difference (voltage) of a transformer based on:
- Number of turns on the primary and secondary coils
- Input potential difference (voltage)
True or False?
The equation for the ratio of potential differences across the primary and secondary coils of a transformer is $V_{s} V_{p} = N_{s} N_{p}$ .
True.
The equation for the ratio of potential differences across the primary and secondary coils of a transformer is $V_{s} V_{p} = N_{s} N_{p}$ .
What is the equation for calculating the output potential difference of a transformer?
The equation for calculating the output potential difference of a transformer is $V_{s} = \frac{N_{p}}{N_{s}} \times V_{p}$
Where:
- $V_{s}$ = output potential difference, measured in volts (V)
- $N_{s}$ = the number of turns on the secondary coil
- $V_{p}$ = input potential difference, measured in volts (V)
- $N_{p}$ = the number of turns on the primary coil

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