4.7.2 The motor effect (might come up) 2 P2

Question 1

What criteria must be met for the equation linking force, magnetic flux density, current and length to hold

Answer 1

The conductor must be placed at right-angles to the magnetic field it is placed in

Question 2

What is the unit for magnetic flux density

Answer 2

Tesla

T

Question 3

How does an electric motor work

Answer 3

A coil of wire, carrying a current is placed in a magnetic field
The forces on the two sides perpendicular to the field experience forces in opposite directions
This causes a rotational effect

Question 4

How do loudspeakers make use of the motor effect

Answer 4

The motor effect is used to convert variations in the current of an electrical circuit into the pressure variations which produce audible sound

Question 5

Explain how a loudspeaker works

Answer 5

A cone with a wire wrapped around it is connected to an a.c power supply and is placed in a permanent magnetic field
When current flows through the wire, it creates a second magnetic field, which interacts with the permanent field
This produces a force which causes the cone to vibrate

Question 6

How is the pitch of the sound from a loudspeaker changed

Answer 6

The frequency of the a.c current is altered

This creates a different frequency vibration in the cone