Magnetism and the Motor Effect Flashcards
At which part of a magnet are the magnetic forces strongest?
The poles of the magnet
What happens when two magnets are brought close to each other?
The exert a force on each other
What type of force is exerted if two like poles of a magnet are brought near each other?
A repulsive, non-contact force
What type of force is exerted if two unlike poles of a magnet are brought near each other?
An attractive, non-contact force
What is a magnetic field?
The region surrounding a magnetic where another magnet or magnetic material experiences a non-contact force
What is the difference between a permanent magnetic and an induced magnet?
A permanent magnet produces its own whereas induced magnet becomes magnetic when placed in a magnetic field
What type of force do induced magnets always cause?
A force of attraction
What is the effect when an induced magnet is removed from a magnetic field?
The induced magnet loses most/all of its magnetism
What are some examples of magnetic materials?
Iron, steel, cobalt and nickel
What can always be said about the force between a magnet and a magnetic material?
Always attractive
How does the strength of a magnetic field alter as you move further away from the magnet producing it?
The magnetic field strength decreases the further you move away
In what direction does a magnetic field point?
In the direction of the force that a North Pole would experience if placed in the field (from the north seeking pole to the south seeking pole of a magnet)
What does a magnetic compass contain?
A small bar magnet that points in the direction of the Earths magnetic field
What is produced when current flows through a conducting wire?
A magnetic field is produced around the wire
What determines the strength of the magnetic field around a current-carrying wire?
The magnet use of the current flowing through the wire
Does a high concentration of field lines mean the field is strong or weak?
Strong
How is a plotting compass used to map out a magnetic field?
Place a compass on a piece of paper near the field, draw an arrow in the direction the compass point, repeat at different points on the paper and join the arrows to make a complete field pattern
What is a solenoid?
A coil of wire which when current passes through relates a strong magnetic field
What is the magnetic field found inside a solenoid like?
Strong and unifirm
Why is the field outside of a solenoid weak?
The fields from each coil cancel out making the outside fields weak
What is an electromagnet?
A solenoid with an added iron core and adding the iron core increases the strength of the magnetic field
What is the motor effect?
When a force is exerted between a magnetic field and a current-carrying conductor placed in that field
What rule is used to determine the force produced by the motor effect?
Fleming’s Left-Hand Rule
When using Flemings left hand rule what does the forefinger represent?
The forefinger points in the direction of the magnetic field
When using Flemings left hand rule what does the second finger represent?
The second points in the direction of current flow in the conductor
When using Flemings left hand rule what does the thumb represent?
The thumb points in the direction of the force produced by the motor effect
What factors affect the size of the force on a current-carrying wire in a magnetic field?
The magnitude of the current flowing through the conductor and the strength of the magnetic field that the conductor is placed in
If the direction of current in a current-carrying wire placed in an uniform magnetic field is reversed, what happens to the force?
The direction of the force is reversed
If the strength of current in a current-carrying wire placed in an uniform magnetic field is increased, what happens to the force?
The strength of the force is increased
What is the equation of force?
Force = magnetic flux density x current x length
What criteria must be met for the equation linking force, magnetic flux density, current and length to hold?
The conductor must be at right-angles to the magnetic field it is placed in
What is the unit used for magnetic flux density?
Tesla
If the current and the magnetic field are parallel to each other, which direction would the force act in?
No force will act
How does an electric motor work?
A coil of wire, carrying a current, is placed in a magnetic field, the forces on the two sides perpendicular to the field experience forces in opposite directions and causes a rotational effect
How are electric motors kept rotating?
A split ring commutator is used, this switches the current direction every half turn, which ensures that the coil keeps spinning
