# P3; Keeping things moving

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• Created by: Joods2204
• Created on: 20-01-16 19:25
What is electromagentic induction?
If an electrical conductor such as a wire cuts through a magnetic field, a potential difference is induced (made to happen) across the ends of the conductor. If the conductor is part of a complete circuit, an electric current will flow in the circuit
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For electromagnetic induction to happen, the conductor must cut through the magnetic field. How can this be achieved?
A conductor can be moved in a magnetic field. A magent can be moved in a coil of wire
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When doesn't electromagnetic induction occur?
If the conductor moves in the same direction as the magnetic field
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What can the induced potential difference be increased by?
Moving the magnet or wire faster. Using a stronger magnet. Increasing the number of turns or loops on the coil. Increasing the surface area of the coil
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What does a transformer do?
Changes the potential difference of electricty
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What does a step-down transformer do?
Reduces the potential difference
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What does a step-up transformer do?
Increases the potential difference
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What is the structure of a transformer?
Soft iron core with two coils of insulated wire wrapped separately around it.
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What is the primary coil connected to?
An a.c supply
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What does the primary coil act like?
An electromagnet
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What happens at the secondary coil?
An alternating potential difference is induced
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How does a transformer work?
Alternating current passes through the primary coil and produces a magentic field that changes direction. The core increases the strength of the magnetic field. The secondary coil cuts through the field, inducing an alternating p.d across the coil
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Why does the circuit have to be connected for a transformer to work
An alternating current only flows if a circuit is connected to the secondary coil.
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Step-up transformers have more turns on what
Their secondary coil
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Step-down transformers have more turns on what
Their primary coil
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Where are switch mode transformers often found?
Often found in power supplies of electronic devices such as laptop and mobile phone chargers
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How is a magnetic field created?
When an electric current flows through a wire
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Why do electromagnets have strong magnetic fields?
Due to the coiling of wire around a soft iron core
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What happens when a magnetic field from a wire is placed into another magentic field?
It causes the wire to move
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What caues a speaker cone to vibrate?
The electric current from the amp is changing direction which causes the magnetic field around the electromagnet to change. The changing attraction & repulsion between the 2 fields make the magnet move back & forth. This moves the speaker cone
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What generates the sound waves in a speaker?
When the speaker cone vibrates, it generates the sound waves
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What is the motor effect?
When an electric current flows through a coil in a simple electric motor, the coil experiences a force and moves
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The force created by the motor effect, is greatest in what conditions?
When the wire is perpendicular to the magnetic field of the permanent magnet
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Name each finger of the Fleming Left Hand Rule
Thumb- movement. Forefinger- Field. Second finger- current
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What can be used to make an electric motor?
A coil of wire that is free to rotate between two opposite magnetic poles
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Describe how an electric motor works
When an electric current flows through the coil, the coil experience a force and moves. One side moves up and the other side moves down.
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In an electric motor, why must the direction of the current be reversed every half turn
Because the coil would stop.
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What can increase the size of the force on a wire carrying a current in a magnetic field
Increasing the size of the current. Increasing the strength of the magnetic field
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In an electric motor, what would increase the speed
By either increasing the size of the current or by increaing the strength of the magnetic field
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Name one way that electromagnets can be used
Cranes
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## Other cards in this set

### Card 2

#### Front

For electromagnetic induction to happen, the conductor must cut through the magnetic field. How can this be achieved?

#### Back

A conductor can be moved in a magnetic field. A magent can be moved in a coil of wire

### Card 3

#### Front

When doesn't electromagnetic induction occur?

### Card 4

#### Front

What can the induced potential difference be increased by?

### Card 5

#### Front

What does a transformer do?