# what I need to learn

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• Created by: jxssann
• Created on: 12-02-19 17:51

## what I need to learn

A magnetic field is where a magnetic material feels a non-contact force.

Compasses point to the south side of a magnet but face north when not near a magnet due to the earths magnetic field.

Permanent magnets produce their own magnetic field whereas induced magnets are magnetic materials that turn into a magnet when put in a magnetic field.

If a current flows through a wire a magnetic field is created around it made from concentric circles perpendicular to the wire.

Use the right hand thumb rule to see the direction of the magnetic field.

A solenoid is a coil of wire, field lines around each loop of wire line up with eachother. The magnetic field inside the solenoid is strong and uniform.

Put a block of iron in in the solenoid to increase the field strength, the iron core becomes an induced magnet. This is called an electromagnet,

Electromagnets are used in scrap yards to pick up, move and drop cars. They can be used within circuits to act as switches. When the switch is closed it turns on the electromagnet that attracts the iron contact on the rocker. The rocker pivots and closes the contacts which turns on the motor.

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## what I need to learn

Current carrying wire inbetween two poles. magnetic field around wire interacts with the magnetic field it has been put in. The magnet and the conductor exert a force on eachother. This causes the motor to kove and is called ' the motor effect.'

The resulting force is upwards. The wire has to be at 90 degrees to the magnetic field.

Calculating the size of the force- Force= magnetic flux density x current x length

Fleming's left-hand rule-  first finger in direction of field, second finger in direction of current, thumb will point in direction of the force

Shows if current or magnetic field are reversed the direction of the force will be reversed.

A current-carrying coil of wire rotates in a magnetic field. We learn about a basic dc motor. forces act on the two side arms of the wire. Coil is on a spindleand one force acts up, one acts down. This makes it rotate.The split ring commutator swaps the contacts every half turn.

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## what I need to learn

Current carrying wire inbetween two poles. magnetic field around wire interacts with the magnetic field it has been put in. The magnet and the conductor exert a force on eachother. This causes the motor to kove and is called ' the motor effect.'

The resulting force is upwards. The wire has to be at 90 degrees to the magnetic field.

Calculating the size of the force- Force= magnetic flux density x current x length

Fleming's left-hand rule-  first finger in direction of field, second finger in direction of current, thumb will point in direction of the force

Shows if current or magnetic field are reversed the direction of the force will be reversed.

A current-carrying coil of wire rotates in a magnetic field. We learn about a basic dc motor. forces act on the two side arms of the wire. Coil is on a spindleand one force acts up, one acts down. This makes it rotate.The split ring commutator swaps the contacts every half turn.

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## what I need to learn

Loud speakers use electromagnets and work because of the motor effect. AC sent through coil of wire attached to the base of a paper cone. Coil surrounds one pole of a permanent magnet and is surrounded by the other so the current causes a force on the coil and it moves. When the current reverses the force acts in the opposite direction and so does the cone.

Variations in current make the cone vibrate so the air around it vibrates so variations in pressure result in sound waves. The frequency of the soundwave is the same as the frequency of the AC.

the generater effect: the induction of a potential difference in a wire which is moving relative to a magnetic field or experiencing a change in the magnetic field.

Causes a pd in a conductor and a current if its part of a complex circuit.

Do this by moving a magnet in a coil of wire/moving a conductor in a magnetic field. if poles of magnet are reversed the pd will be too.

same effect, magnet in coil. spin round and magnetic field changes. this includes a pd that makes current flow.after half a turn the mf reverses and so does everything else. this continued will cause an AC.

transformers change the pdof an AC. two wire coils joined with an iron core. Alternating pd across primary, iron core magnetises and demagnetises quickly. this causes an alternating pd in secondary coil

step up- more turns on secondary. step up pd.

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