Magnetic Fields

Question 0

What is the condition for a current carrying wire to feel a force in a B field?

Answer 0

The wire must cut the field lines at 90 degrees.

Question 1

What do field lines show?

Answer 1

The direction of acceleration of a south seeking/ ‘free’ North Pole.
(Direction of the field strength)

Question 2

When is Flemings left hand rule used?

Answer 2

When current is already flowing in a circuit.

Question 3

When is Flemings right hand rule used?

Answer 3

When you’re inducing a current in the circuit.

Question 4

A coil of wire will feel a pair of forces as the current changes direction. Couple of forces, causes rotation. What is the name of the equipment that uses this principle?

Answer 4

Electric Motor.

Question 5

What are the conditions for a particle to feel the Bev force?

Answer 5

It must be:

• Moving (v)
• Charged (q)
• Moving at 90 degrees to the field.

And there must be a magnetic field present. (b)

Question 6

What is different about the second finger of Flemings LHR for a singular electron?

Answer 6

Opposite direction did to conventional flow of current.

Question 7

Why does an electron oscillate with uniform circular motion in a magnetic field?

Answer 7

• Magnetic force is always perpendicular to the velocity. Accelerates in direction of force, therefore centripetal acceleration.
• No work is done on the charge.

Question 8

What is the equation for the radius of a charged particle in circular orbit in a magnetic field ?

Answer 8

R= MV/BQ