7: Magnetism and Electromagnetism Flashcards
What is the difference between permanent and induced magnets.
A permanent magnet produces its own magnetic field.
An induced magnet is a material that becomes a magnet when it is placed in a magnetic field.
What is a magnetic field?
The region around a magnet where a force acts on another magnet or on a magnetic material (iron, steel, cobalt and nickel) is called the magnetic field.
How does an electromagnet work.
When a current flows through a conducting wire a magnetic field is produced around the wire.
Shaping a wire to form a solenoid increases the strength of the magnetic field created by the current in the wire. The magnetic field inside a solenoid is strong and uniform.
Adding an iron core increases the strength of the magnetic field of a solenoid.
An electromagnet is a solenoid with an iron core.
What are the poles of a magnet?
The points of the magnet where the magnetic force is at its strongest.
There is a positive pole and a negative pole on opposite sides of the magnet.
Like poles repel each other and opposite poles attract.
How is the direction of the magnetic field defined?
The direction of the magnetic field at any point is given by the direction of the force that would act on another north pole placed at that point.
The direction of a magnetic field line is from the north (seeking) pole to the south (seeking) pole of the magnet.
What is Fleming’s left-hand rule?
When a conductor carrying a current is placed in a magnetic field, the magnet producing the field and the conductor exert a force on each other. This is called the motor effect.
A coil of wire carrying a current placed in a magnetic field tends to rotate. This is the basis of an electric motor.
What is the equation for calculating the force between a magnet and a conductor?
F = BIlsinθ
F: force (newtons, N)
B: magnetic flux density (tesla, T)
I: current (amperes, A)
l: length (metres, m)
θ: angle between magnet and conductor
(When the angle between the magnet and conductor is a right angle, ignore sinθ from the equation. (sin(90) =1))
