magnetism and electromagnetism Flashcards
(18 cards)
Give examples of magnetic materials
-Iron
-Cobalt
-Nickel
-Steel
What is a permanent magnet?
An object with its own magnetic field
In which direction do field lines travel?
North to south
Where is the magnetic field strongest?
At the poles
What is an induced magnet?
An object will become magnetised when placed in a strong magnetic field
What does the strength of a magnetic field depend on in an electromagnet?
The strength of the magnetic field depends on the current through the wire and the distance from the wire
What is a solenoid?
A coil of wire
What is an electromagnet?
A solenoid with an iron core
What is the motor effect?
When a current carrying wire is placed in a permanent
magnetic field they exert a force on each other
Which factors affect the size of the force in a motor?
-the size of the current
-the strength of the permanent magnet (the magnetic flux
density)
-the length of the wire
What does each finger in Flemming’s left hand rule?
First finger is the magneticField
seCond finger is the Current
thuMb is the force (Movement)
What is the generator effect?
A wire moving in a magnetic field induces a potential difference between the 2 ends of the wire. If the wire is part of a circuit a current will flow
Which factors affect the size of induced potential difference in a generator?
-the strength of the magnetic field
-length of the wire in the solenoid
-force of the movement
What affects the direction of induced current?
The direction of the magnetic field and the direction of the movement
Which effect does an alternator use?
The generator effect to produce a.c
Which effect do dynamos use?
The motor effect to produce d.c
How do loudspeakers work?
Loudspeakers use the motor effect. The cone of the speaker is attached to a solenoid that is placed in a permanent magnet field. Changes in the current supplied to the solenoid affect the force between the magnet and the solenoid causing it to move backward and forwards; this move the speaker cone in and out creating sound (pressure) waves
How do microphones work?
A microphone uses the generator effect (works the opposite
way to a speaker). The sound waves move a cone in and
out. This is attached to a solenoid in a permanent magnetic field; the movement of the solenoid induces a changing p.d., and therefore an a.c.
