6- Magnetism + Electromagnetism Flashcards
What are properties of magnetically soft materials?
- easy to magnetise
- easily lose their magnetism
- temporarily magnetised
What are some properties of magnetically hard materials?
- difficult to magnetise
- do not easily lose their magnetism
- permanently magnetised
What are permanent magnets made out of?
Magnetically hard materials
What are electromagnets made out of?
Magnetically soft materials
What is a magnetic field?
The region around a magnet where a force acts on another magnet or on a magnetic material
When is a uniform filed created?
when two opposite poles are held close together
What are examples of magnetic materials?
Iron
Cobalt
Nickel
Steel
What are properties of permanent magnets?
- do not lose their magnetism
- produce their own magnetic fields
What is an induced magnet?
When a magnetic material is placed in a magnetic field - can lose magnetism quickly
What is electromagnetism?
When a current flows through a conducting wire a magnetic field is produced around the wire
How can you make the magnetic field stronger?
Increase current
More coils
How does the motor effect occur?
When two magnetic fields interact to produce the force on the wire
Explain the motor effect?
- when the two magnetic fields interact, each side of the coil feels a force in opposite directions
- the coil rotates
- the commutator changes direction of current in the coil every half turn
- current flows in same direction relative to permanent magnet
How can the speed at which the coil rotates be increased by: (in motor)
- Increasing the current
- Increasing the strength of the magnetic field
How can the direction of rotation of coil in the motor be changed by?
- Reversing the direction of the current
- Reversing the direction of the magnetic field by reversing the poles of the magnet
How can the force supplied by the motor be increased by?
- Increasing the current in the coil
- Increasing the strength of the magnetic field
- Adding more turns to the coil
What does a loudspeaker consist of?
a coil of wire which is wrapped around one pole of a permanent magnet
How does a loudspeaker work?
- An ALTERNATING current passes through the coil creating CHANGING magnetic field around the coil
- current is constantly changing direction, + direction of the magnetic field,
- The magnetic field produced around the coil interacts with the field from the permanent magnet
- The interacting magnetic fields will exert a force on the coil
- the coil then oscillates, creating sound waves
How can a wire experience full force?
The wire needs to be 90 degrees to the magnetic field
How does the force on a wire act?
In the same direction relative to the magnetic field of the magnets and the direction of the current in the wire.
The magnitude of the force increases with ….?
The strength of the magnetic field
Reversing the current or the magnetic field also reverses the …?
Direction of the force
The force increases with the…?
Amount of current passing through the conductor
When will a charged particle not feel a force?
When the motion is parallel to the field
Give examples of uses for electromagnets and electric motors?
Bells, loudspeakers + headphones
What is Electromagnetic induction?
When a voltage is induced in a conductor or a coil when it moves through a magnetic field or when a magnetic field changes through it.
How does the generator effect take place?
by the conductor or coil cutting through the magnetic field lines of the magnetic field
When will a potential difference be induced in the conductor?
if there is relative movement between the conductor and the magnetic field
If the conductor is part of a complete circuit then where is the current induced
In the conductor
What is a simple alternator
a type of generator that converts mechanical energy to electrical energy in the form of alternating current
What does a basic transformer consist of ?
A primary coil
A secondary coil
An iron core
What does a transformer do ?
- An alternating current (which changes direction) supplied to the primary coil
- the changing magnetic field passes through the iron core
- there is now a changing magnetic field inside the secondary coil
- changing field cuts through the secondary coil and induces a potential difference
- If the secondary coil is part of a complete circuit it will cause an alternating current to flow
What does a step up transformer have ?
More turns on the secondary coil than the primary coil
What do step up transformers do to the voltage?
Increase the voltage
What do step down transformers do to voltage ?
Decrease the voltage
What does a step down transformer have?
More turns on the primary coil than the secondary
What is a step up transformer used for across the country?
To boost the voltage before it is transmitted
What is a step down transformer used for across the country?
To reduce the voltage so it is more useful and safer to use
