Magnetism (Paper 2) Flashcards
Define a magnetic field
- A region where other magnets or magnetic materials experience a force
What type of force is a magnetic force
- Non-contact
Where is the magnetic field the strongest
- At the poles of the magnets
Where is the magnetic force the strongest
- At the poles of the magnet
What direction is the force between a magnet and a magnetic material
- Attractive
What are the two types of magnets
- Permanent
- Induced
Define a permanent magnet
- A magnet that produces its own magnetic field
Define an induced magnet
- A magnetic material that becomes a magnet when it is put into a magnetic field
What type of force is always occurs between a permanent and induced magnet
- An attractive force
What happens when an induced magnet is no longer within a magnetic field
- The induced magnet quickly loses its magnetism and stops producing a magnetic field
What happens (relative to magnetism) when a current flows through a wire
- A magnetic field is created around the wire
What makes up the magnetic field of a wire with current flowing through it
- Concentric circles perpendicular to the wire with the wire as the centre
Define concentric circles
- Circles that share the same centre
What happens to the magnetic field of a wire when you change the direction of current
- You change the direction of the magnetic field
What factors affect the strength of the magnetic field of an electromagnet
- The size of the current flowing through the wire
- The distance from the centre of the magnetic field
Define a solenoid
- A coil of wire that can create a magnetic field when an electric current passes through it
What are the properties of the magnetic field within a solenoid
- Strong
- Uniform
How can you increase the magnetic field strength of a solenoid
- Placing a block of iron in the centre of the solenoid, which becomes an induced magnet
What name is given to a solenoid with an iron core
- Electromagnet
Uses of electromagnets
- In circuits as switches
- To pick things up
- Headphones and speakers
Define the motor effect
- When a current carrying wire is placed between magnetic poles, the conductor and the magnet exert a force on each other
What does the motor effect cause
- Movement of the wire
What conditions are required for a wire to experience the full force of the motor effect
- The wire must be 90 degrees to the magnetic field
What happens to the force of the motor when the wire runs parallel to the magnetic field
- The force is nullified
What direction is the force always exerted in the motor effect
- At a right angle to the magnetic field of the magnets and the direction of current in the wire
What factor affect the size of the force in the motor effect
- The strength of the magnetic field
- The amount of current passing through the conductor
What factors affect the force acting on a conductor in a magnetic field
- Magnetic flux density
- Size of the current through the conductor
- The length of the conductor in the field
What conditions are required to use the equation for the force in the motor effect
- When the flow of current is 90 degrees to the magnetic field it is in
What do the fingers correspond to in the Fleming left hand rule
- Thumb corresponds to the direction of the force
- First finger corresponds to the direction of the magnetic field
- Second finger corresponds to the direction of current
Function of a split-ring commutator
- Swaps the contacts every half turn to keep the motor rotating in the same direction
How can the direction of a motor be reversed
- Swapping the polarity of the DC supply (reversing the current)
- Swapping the magnetic poles (reversing the field
Define the generator effect
- The induction of a potential difference (and current if there is a complete circuit) which is moving relative to a magnetic field, or experiencing a change in magnetic field
What does the generator effect cause
- A potential difference in a conductor, as well as a current if the conductor is part of a complete circuit
