Magnetic Fields (Module 24) Flashcards
What is a line of force?
This is a line along which a north pole would move in the field.
What is the motor effect?
A current carrying wire placed at a non-zero angle to the lines of force of an external magnetic field experiences a force due to the field.
Tell me how Fleming’s Left - hand rule works?
Thumb facing up = Motion
First finger straight = Magnetic Field
Second finger perpendicular to the first = Current
What is the force of a wire proportional to?
1) Current
2) Length of the wire
Define Magnetic Flux Density
Sometimes referred to as the strength of the magnetic field.
This is defined as the force per unit length per unit current on a current-carrying conductor at right angles to the magnetic fields.
What is the unit of B?
Tesla which equals 1 N/m/A
What does a simple electric motor consist of?
a coil of insulated wire which spins between the poles of a U-shaped magnets.
What happens when a direct current passes round the coil?
The wires at opposite edges of the coil are acted on by forces in opposite directions.
-The force on each edge makes the coil spin about its axis.
Describe the direction of the Earth’s magnetic field at the magnetic north pole.
It is vertically downards.
What do we use to measure flux density?
Hall Probes
What is the Cyclober…I mean cyclotron?
This is used in hospitals to produce high energy beams for radiation therapy. It consists of two hollow D-shaped electrodes in a vacuum chamber. With a uniform magnetic field applied perpendicular to the planes of the dees, a high-frequency alternating voltage is applied between the dees.
