Electromagnetism And Electrodynamics

Question 1

How do you apply the right hand wire rule?

Answer 1

Physically do it: thumb pointing in the direction of conventional current and your fingers curling in the direction of the magnetic field around the wire.

Question 2

Superposition principle (applied to a loop)?

Answer 2

The net magnetic field at any point inside the loop is the sum of the individual magnetic fields caused by all the individual parts of the loop.

Question 3

Solenoid?

Answer 3

A series of turns wound next to each other. On the outside, the field represents that of a bar magnet and inside, the field lines are all parallel.

Question 4

Electromagnets?

Answer 4

Magnetic material that has wire around it for the purpose of their magnetism being switched on and off as needed. They can be much stronger magnets.

Question 5

List at least three types of electromagnets.

Answer 5

Electric motors, loudspeakers, telephones, relay switches, microphones, lifting device of cranes, bells and CAT - scans.

Question 6

Electromagnetic Induction?

Answer 6

Occurs when a solenoid and a magnet move relative to each other, inducing a current. The presence of the current means the solenoid is a voltage source.

Question 7

Magnetic Flux Linkage? What are its two acceptable S.I. units?

Answer 7

The product of the number of turns on the coil and the flux through the coil. T.m² and Wb.

Question 8

Magnetic Flux Density?

Answer 8

A representation of the magnitude and direction of the magnetic field.

Question 9

Faraday’s Law of Electromagnetic Induction?

Answer 9

The emf induced is directly proportional to the rate of change of magnetic flux.

Question 10

Lenz’s Law?

Answer 10

The induced current flows in a direction so as to set up a magnetic field to oppose the change in magnetic flux.

Question 11

Generator?

Answer 11

An electrical machine that converts mechanical energy into electrical energy by changing the magnetic flux through a coil.

Question 12

What are the parts of a AC generator?

Answer 12

The coil, the magnet, the slip rings, the carbon brushes, the terminals and the rotating mechanism.

Question 13

What are the parts of a DC generator?

Answer 13

The coil, the magnet, the split ring commutator, the carbon brushes, the terminals and the rotating mechanism.

Question 14

What do your 3 fingers represent when utilizing the right hand generator rule?

Answer 14

Thumb: Motion.
First finger: Magnetic field (North to South).
Second finger: Current direction.

Question 15

How can the emf and current be increased?

Answer 15

By increasing the number of turns in the coil (N). By using a stronger magnet (increasing B). By increasing the area (A) enclosed by the coil. Lastly, by turning the generator coil faster.

Question 16

Motor?

Answer 16

An electrical machine that functions by transforming electrical energy into mechanical energy.

Question 17

What do your 3 fingers represent when utilizing the left hand motor rule?

Answer 17

Thumb: Motion
First finger: Magnetic field (North to South).
Second finger: Current direction.

Question 18

What are the parts of an AC motor?

Answer 18

The AC source, the coil, the magnet, the slip rings and the carbon brushes.

Question 19

What are the parts of a DC motor?

Answer 19

The DC source, the coil, the magnet, the split ring commutator and the carbon brushes.

Question 20

What is the main difference between generators and motors.

Answer 20

Generators transform mechanical energy into electrical energy and motors transform electrical energy into mechanical energy.

Question 21

Ideal transformers and Realistic transformers?

Answer 21

Ideal transformers convert 100% of input power to output power. However in realistic transformers, input power is greater than output power.

Question 22

Efficiency?

Answer 22

The ratio of output power to input power.

Question 23

How does a transformer work?

Answer 23

When alternating current flows through the primary coil, a changing magnetic field is induced. This changing magnetic field is transferred through the iron core to the secondary coil. Where it creates a changing electric field in the secondary coil that then induces an emf and current in the secondary coil.

Question 24

Advantages of AC over DC?

Answer 24

(1) Electrical energy can be transmitted over long distances with much smaller energy losses using AC than DC. (2) Transformers work with AC current. (3) DC carbon brushes require frequent replacing.