Magnetic Fields

Question 1

What is magnetic flux density?

Answer 1

Magnetic flux density B of a magnetic field is defined as the force per unit current per unit length on a wire placed at 90º to the direction of the magnetic field

Question 2

What is the tesla?

Answer 2

A flux density of 1T causes a force of 1N to be exerted on every 1m length of wire carrying a current of 1A in a direction perpendicular to the field.

Question 3

On a solenoid, what direction would the current be at a North pole?

Answer 3

Anti-clockwise

Question 4

On a solenoid, what direction would the current be at a North pole?

Answer 4

Clockwise

Question 5

How does a cyclotron work?

Answer 5

A cyclotron consists of two hollow D-shaped electrodes known as dees. An alternating electric field is maintained across the gap between the two sides by an alternating potential difference. A constant uniform magnetic field acts through the whole of the accelerator (perpendicular).

The charged particles to be accelerated are injected into the dees from their source at the center of the cyclotron. The magnetic force, BQv provides a centripetal force to make the particles follow a circular path, so that they repeatedly pass through the gap between the dees.

Each time a particle passes through the gap, it is accelerated by the electric field and moves faster, so spirals further outwards as r is proportional to v. When the radius of the path of charged particles reaches the radius of the dees, the particles exit the cyclotron and strike the target material

Question 6

Why is an alternating p.d. used in a cyclotron?

Answer 6

An alternating p.d. is used to reverse the direction of the electric field in order to accelerate the particle after every half cycle