Magnetism And Electromagnetism

Front 1

What do all electric currents in a wire produce?

Back 1

A circular magnetic field

Front 2

How does the right hand grip rule work for a wire?

Back 2

Thumb points in direction of current and fingers curl in direction of field (N to S)

Front 3

How do you increase the strength of a magnetic field around a current carrying wire?

Back 3

Inc current
Wrapping wire into solenoid
Using thicker wire

Front 4

How do you make a solenoid?

Back 4

Wrap insulated wire into a coil making the field stronger

Front 5

How does the right hand grip rule for solenoids work?

Back 5

Right hand fingers curl in current direction and thumb points north

Front 6

How do you increase the strength of a field in a solenoid?

Back 6

Inc current
Thicker wire
Inc number of coils
Wrap around magnetically soft core

Front 7

What is an electromagnet

Back 7

A coil of wire wrapped around a magnetically soft core

Front 8

Advantages of electromagnet over permanent?

Back 8

Can be switched on and off
Strength can be increased by inc number of turns and inc current

Front 9

How do you predict force in magnetic fields?

Back 9

Flemings left hand rule

Front 10

Explain flemings left hand rule

Back 10

Force in thumb
Field from first finger (N to S) Current in second finger (+ve to -ve)

Front 11

Explain the motor effect

Back 11

Any charged particle in a magnetic field experiences a force providing it isnt moving parallel to the magnetic field.

Front 12

Why does the motor effect happen?

Back 12

The magnetic field produced by the charged particle interacts with the magnetic field of the magnet.

Front 13

How do you increase the force in a wire?

Back 13

Inc current
Increase magnetic field strength

Front 14

Describe how a loudspeaker works

Back 14

The current flowing through the coil is at 90° to the magnetic field.
It experiences a force (right or left)
This moves the cone
With an AC current, the direction reverses, reversing the force direction
This happens many times a second causing the cone to vibrate, producing a sound with the same frequency as the AC current producing it.

Front 15

Larger current in a loudspeaker =

Back 15

larger force, greater movement of cone and louder sound

Front 16

Increasing AC frequency in a loudspeaker...

Back 16

Increases the pitch

Front 17

Describe how a DC motor uses the principles from the motor effect.

Back 17

The magnetic field produced by the current interacts with the magnetic field of the magnet producing a force which acts on the wire making it move.
It rotates because current flowing in opposite directions in parallel wires produces forces in opposite directions and these are not in the same straight line.
One side experiences upward force and the other side downward.
The coil rotates and after 90° the commutator halves swap contact from one brush to the other.
This reverses the current through the coil, reversing the forces on each side, continuing rotation.
Without the commutator the coil would stay in a vertical position, with equal forces acting in opposite positions.

Front 18

How do you increase the rotation speed of a motor

Back 18

Increasing magnetic field strength (coil is wound onto soft iron armature)
Increasing number of turns
Increasing the current

Front 19

What material would you use for the brushes of the commutator?

Back 19

Carbon

Front 20

What effect does a larger mass have on the acceleration of force produced?

Back 20

The higher the mass of an object, the smaller the acceleration the force will produce.