Physics: Electricity and Magnetism

Question 1

Motor effect

Answer 1

A moving charge in a magnetic field will experience a force (Lorentz force).
The force will be perpendicular to both the velocity of the charge and the magnetic field direction.
F = qvB

Question 2

Function of a split ring commutator

Answer 2

reverses the direction of the current within the rotating loop every 180 degrees
indicative of a DC motor

Question 3

Parts of a DC motor

Answer 3

1. split ring commutator
2. carbon brush
3. rotating loop
4. DC power supply

Question 4

Function of a carbon brush

Answer 4

conducts electricity

low friction

Question 5

Energy conversion in a motor

Answer 5

electrical –> mechanical

Question 6

Faraday’s Law

Answer 6

An induced emf is directly proportional to the number of turns in a coil (N) as well as the rate of change of magnetic flux.

Question 7

Energy conversion in a generator

Answer 7

mechanical –> electrical

Question 8

Lenz’s Law

Answer 8

The induced current will create a magnetic field that opposes the change in magnetic flux.
(Changing magnetic flux induces a current; changing current induces its own magnetic field)

Question 9

Key differences between a DC and AC generator

Answer 9

1. type of current produced
   - AC generator produces current that changes direction
2. AC generator uses SLIP rings
3. DC generator uses SPLIT rings

Question 10

Advantages of Alternating current (AC)

Answer 10

Can step up or step down voltage