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What is the link between movement, magnetism and electric current?
Electromagnetism and movement
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Wire in a magnetic field
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The direction of the force acting on a wire in an electromagnetic field can be reversed by:
The direction of the force is therefore relative to both the direction of the magnetic field and the current.
reversing the current reversing the magnetic field
Changing the direction of the force
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It is possible to predict the direction of the force acting on a wire – its motion – if the direction of the current or the magnetic field are known. Fleming’s left-hand rule is used to do this.
Fleming’s left-hand rule
thuMb = Motion
First finger = magnetic Field
seCond finger = Current
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Increasing the size of the force
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Coil in a magnetic field
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The motor effect: true or false?
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What are electric motors?
How many items do you own that contain an electric motor?
An electric motor is a device that converts electrical energy into mechanical energy to produce a turning effect.
Most motors are powered using direct current (DC), which is produced by cells and batteries.
Motors powered by mains electricity use alternating current (AC). These motors use electromagnets rather than permanent magnets.
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How does an electric motor work?
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DC electric motor simulation
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Would the same strength motor be used in both of these?
How can the strength of an electric motor be increased?
How do we increase motor strength?
increase the strength of the magnet
increase the current flowing through the coil
increase the number of turns on the coil
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Inducing current in a wire
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It is possible to predict the direction of the induced current produced by a generator if the direction of the force (or motion) or the magnetic field are known. Fleming’s right-hand rule is used to do this.
Fleming’s right-hand rule
First finger = magnetic Field
seCond finger = Current
thuMb = Motion
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What is electromagnetic induction?
When current flows through a wire held in a magnetic field, a force is created that moves the wire.
The opposite is also possible: if a wire is moved across a magnetic field, a current is produced. This is called electromagnetic induction.
Induction also occurs if a magnet is moved in a coil of wire, or if a coil of wire rotates in a magnetic field.
In all these methods of inducing a current, the wire and magnetic field move perpendicular to each other. If they move parallel to each other, no current is induced.
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Inducing current in a coil
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A generator is a device that converts mechanical energy into electrical energy. It is the opposite of an electric motor.
Power stations use generators to produce electricity on a large scale. Mechanical energy is provided by rotating turbines that can be powered by:
What are generators?
high-pressure steam – in coal, oil, gas and nuclear power stations
wind – in wind turbines
falling water – in hydroelectric power stations
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How do AC generators work?
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AC generator simulation
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How can the size of an induced current be increased?
In a power station generator, an electromagnet is often used as this can provide a stronger magnetic field than is possible with a permanent magnet.
Increasing the size of the induced current
increase the speed at which the coil rotates
increase the strength of the magnetic field
increase the number of turns in the coil
increase the total area of the coil.
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Factors affecting induced current
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Induction: true or false?
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alternating current – A current that constantly changes direction. It is produced by most electrical generators.
commutator – The part of a motor that enables the coil to rotate using direct current.
direct current – A current that always flows in the same direction. It is produced by cells and batteries.
generator – A device that converts mechanical energy into electrical energy.
induction – Generating a current in a wire by moving the wire in a magnetic field, or by moving a magnet inside a coil.
motor – A device that converts electrical energy into mechanical energy.
slip rings – The parts of a generator that enable the rotating coil to produce alternating current.
Glossary
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Anagrams
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Multiple-choice quiz