A bar magnet is a permanent magnet because it is always magnetic.
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What are some magnetic metals?
iron, nickel, steel, cobalt
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What are the two ends of a bar magnet called?
The north-seeking pole/North Pole (red) and the south-seeking pole/South Pole
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What happens if two magnets are placed close to each other?
The North Pole on one magnet attracts the South Pole on the other.
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What happens if two North poles or two South poles are placed near each other?
The magnets repel each other
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When a piece of magnetic material is in a magnetic field...
It becomes a magnet itself. This is called an induced magnet
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An induced magnet stops being magnetic when...
It is taken out of the field
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Where are magnets used?
In electric motors, generators, loudspeakers, and the other electrical devices, as well as door latches and knife holders
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How can you find the shape or direction of a magnetic field?
By using plotting compasses.
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How does a compass work?
The needle of a compass is a very small magnet. The needle always points to a position near the earth North Pole.
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What causes a magnetic field?
Current flowing through a wire.
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The direction of the magnetic field depends on...
The direction of the current
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The strength of the magnetic field depends on...
The size of the current
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The magnetic field is strongest...
Closer to the wire, and gets weaker with increasing distance
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How can you detect a magnetic field?
we can detect them using iron filings. The tiny pieces of iron line up in a magnetic field.
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What is an electromagnet?
A coil of wire with a current flowing through it
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The magnetic field of an electromagnet can be made stronger by...
Putting a piece of iron (an iron core) inside the coil. This iron becomes a temporary magnet-it is only magnetic while the field from the electromagnet is affecting it
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Why does a magnetic force occur?
Because the current in wire creates a magnetic field around the wire and this interacts with the magnetic field between the magnets.
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What is magnetic flux density?
The strength of the magnetic field (measured in newtons per ampere meter-N/ Am or Tesla-T)
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What is the equation the magnetic flux density?
Magnetic flux density= Force/ Current x Length
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What are transformers used for?
To increase or decrease the voltage of alternating currents.
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A tansformer is usually made using...
Two coils of wire wound onto an iron core.
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What does electromagnetic induction do in a transformer?
A voltage in one coil induces a voltage in the second coil.
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How does a transformer work?
An alternating voltage is applied to the primary coil. This causes an alternating magnetic field to be set up in the core. The secondary coil is in this changing magnetic field and so it has an alternating voltage induced in it.
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The size of the secondary voltage depends on...
the number of turns on both the primary and the secondary coils, and on the size of the AC voltage applied across the primary coil.
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What is the equation for 100% effective transformer?
Potential difference across primary coil x current in primary coil = potential difference across secondary coil x current in secondary coil
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What can the equation for 100%effective transformer also be written as?
Vp x Ip = Vs x Is
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What is a step-up transformer?
a transformer that increases the voltage
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What is stepdown transformer?
a transformer that decreases the voltage
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When a current flows through a wire some energy is lost as...
Heat. The higher the current the more heat is lost. To reduce these losses, the National Grid transmits electricity at a low current.
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Step-up transformers are used at power stations to...
produce the very high voltages needed to transmit electricity through the National Grid power lines. These high voltages are too dangerous to use in the home, so step-down transformers are used locally to reduce the voltage to safe levels.
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Other cards in this set
Card 2
Front
What are some magnetic metals?
Back
iron, nickel, steel, cobalt
Card 3
Front
What are the two ends of a bar magnet called?
Back
Card 4
Front
What happens if two magnets are placed close to each other?
Back
Card 5
Front
What happens if two North poles or two South poles are placed near each other?
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