Separate Physics - 6.7 Flashcards
Where, in a magnet, is the magnetic force the strongest?
The poles
What happens when two magnets are brought closer together?
They exert a force on one another
What do two like poles do?
They repel each other
What do two unlike poles do?
They attract each other
What is attraction and repulsion between two magnetic poles an example of?
Non-contact force
What does a permanent magnet produce?
Its own magnetic field
What is an induced magnet?
A material which becomes a magnet when it is placed in a magnetic field
What does induced magnetism cause?
A force of attraction
What happens when an induced magnet is removed from the magnetic field?
Loses most / all of its magnetism quickly
What is the magnetic field?
The region around a magnet where a force acts on another magnet or on a magnetic material
Give some examples of a magnetic material
- Iron
- Steel
- Cobalt
- Nickel
What force exists between a magnet and a magnetic material?
Attraction
What does the strength of a magnetic field depend on?
The distance from the magnet (with the field being strongest at the poles)
How can the direction of the magnetic field be identified?
It is given by the direction of the force which would act on another north pole placed at that point
What is the direction of a magnetic field line?
From the north (seeking) pole to the south (seeking) pole of the magnet
What does a magnetic compass comprise of?
A small bar magnet (pointing towards the Earth’s magnetic field)
What happens when a current flows through a conducting wire?
A magnetic field is produced
What affects the strength of a magnetic field through a conducting wire with current flowing through?
The current through the wire and the distance from the wire
How can the strength of a magnetic field created by a current through a wire be increased?
The wire can be shaped, forming a solenoid (the magnetic field inside a solenoid is strong and uniform)
What is the shape of the magnetic field around a solenoid?
A similar shape to that of a bar magnet
What does an iron core in a solenoid do?
Increases the strength of the magnetic field
What is an electromagnet?
A solenoid with an iron core (it can be turned on and off)
Higher Q. What is the motor effect?
A conductor carrying a current placed in a magnetic field causes the magnet and the conductor to exert a force on one another
Higher Q. What does Fleming’s left-hand rule represent?
The relative orientation of the force, current in the conductor and magnetic field
Higher Q. What does a coil of wire, carrying a current in a magnetic field, tend to do?
Rotate (the basis of an electric motor)
Higher Q. What does the force on a conductor in a magnetic field cause?
The rotation of the coil in an electric motor
Separate Higher Q. How do loudspeakers and headphones use the motor effect?
Converting variations in current in electrical circuits to the pressure variations in sound waves
Separate Higher Q. What is the generator effect?
A potential difference induced across the ends of a conductor, inducing a current
Separate Higher Q. What can cause a potential difference to be induced across the ends of a conductor?
If an electrical conductor moves relative to a magnetic field or there is a change in the magnetic field around a conductor
Separate Higher Q. An induced current generates a magnetic field: what does this oppose?
The original change: either the movement of the conductor or the change in magnetic field
Separate Higher Q. In an alternator, what does the generator effect cause?
AC
Separate Higher Q. In a dynamo, what does the generator effect cause?
DC
Separate Higher Q. How do microphones use the generator effect?
They convert the pressure variations in sound waves into variations in current in electrical circuits
Separate Higher Q. What does a basic transformer consist of?
A primary and secondary coil, wound on an iron core
Separate Higher Q. If a transformer was 100% efficient, what would the electrical power output equal?
The electrical power output would equal the electrical power input
Separate Higher Q. How do transformers use AC?
The effect of an AC in one coil induces a current in another
Separate Higher Q. How does the ratio of the potential differences across the two coils vary?
The potential differences depend on the ratio of the number of turns on each
