Electrical Principles and Technologies Part Three

Question 1

What is energy?

Answer 1

The ability to do work.

Question 2

What is work?

Answer 2

The transfer of energy.

Question 3

What is the Joule?

Answer 3

The unit of measure for energy.

Question 4

What are the four common forms of energy?

Answer 4

1) chemical energy
2) electrical energy
3) mechanical energy
4) thermal energy

Question 5

What is chemical energy?

Answer 5

Stored in chemicals and released when chemicals react. Potential/stored energy in foods, fuels, batteries, explosives.

Question 6

What is electrical energy?

Answer 6

Energy of charged particles, transferred when electrons travel from place to place.

Question 7

What is mechanical energy?

Answer 7

Energy of motion, energy possessed by an object because of its motion or its potential to move.

Question 8

What is thermal energy?

Answer 8

Total kinetic energy of all particles in a substance. The faster a particle moves, the more kinetic energy.

Question 9

What is the 2 cup analogy?

Answer 9

Compare two cups holding equal amounts of water, the one containing more thermal energy will feel warmer.

Question 10

What is energy conversions?

Answer 10

All forms of energy can be converted to other forms.

Question 11

What is the law of conservation of energy?

Answer 11

Energy cannot be created nor destroyed.

Question 12

What is a thermocouple?

Answer 12

A device that converts thermal energy to electricity.

Question 13

What is the Hans Oersted Demonstration?

Answer 13

1820: Compass needle deflected by magnetic field of a current carrying wire. Proved a current flowing through wire creates magnetic field around wire.

Question 14

What did Michael Faraday do in 1831?

Answer 14

Made the first electric motor, proving electromagnetic force can produce continuous motion.

Question 15

What is a permanent magnet?

Answer 15

Hard steel alloy which stays magnetic for a long time.

Question 16

What is an electromagnet?

Answer 16

Coil of wire (usually with iron core) which has magnetic effects when attached to a current; can be turned off and on.

Question 17

How does a simple electro-motor work?

Answer 17

• wrap piece of metal in wire
• hook wires to a battery
• reversing wire reverses the current which reverses the polarity of magnets
• continuous motion

Question 18

What is an armature?

Answer 18

Rotating shaft with a coil wrapped around it.

Question 19

What is a commutator?

Answer 19

A split ring that breaks flow of electricity for a bit then reverses the flow in the coil. If contact if broken, so is the magnetic field.

Question 20

What are the brushes?

Answer 20

They reverse the flow of electricity through electromagnetic coil, make contact with commutator by “brushing” against it.

Question 21

How do the poles work in an electromotor?

Answer 21

Poles of the armature are attracted to opposite poles of a permanent magnet and spin towards it. At 180 degrees contact is broken and the poles reverse. The split-ring commutator break the flow, then reverses the current. Armature keeps spinning due to momentum, brushes break contact again poles keep reversing= continuous motion.

Question 22

What is DC?

Answer 22

Direct current- electrons flow one way (most battery operated things use DC)

Question 23

What is AC?

Answer 23

Alternating Current- electrons move back and forth 60 times/sec (ex.wall outlets)

Question 24

What are transformers?

Answer 24

A current carrying wire is wrapped around one side of an iron ring (core). This is the primary coil. A secondary coil of wire is wrapped around the other side of the core. Current flowing through the primary coil generates an electromagnetic field which induces a current in the secondary coil.

Question 25

What is a step-down transformer?

Answer 25

They reduce voltage. There are more windings on the primary coil than the secondary.

Question 26

What is a step-up transformer?

Answer 26

They increase voltage. There are fewer windings on the primary coil than the secondary.

Question 27

What is a DC generator?

Answer 27

Structurally same as a DC motor. If electricity is passed through a DC generator, it will spin like a motor.

Question 28

What is an AC generator?

Answer 28

As the motor turns, one side of the coil moves up between the magnets, the other side moves down. Current is induced in the coil. As the generator continues to rotate current is induced in the coil in the opposite direction due to slip rings. This reversal of current every 1/2 rotation generates alternating current.

Question 29

What are the types of generators?

Answer 29

• wind
• hydro electric
• steam driven (nuclear, coal, geothermal, biomass)

Question 30

What is power?

Answer 30

The rate at which we use energy. It is measured in watts, also known as 1J/sec.

Question 31

How to calculate power?

Answer 31

P=IV
Power= Current(A)*voltage(V)

Question 32

What is energy?

Answer 32

The ability to do work. Measured in Joules (J).

Question 33

How to calculate energy?

Answer 33

E=Pt
Energy= Power(W)*time (sec)

Question 34

How do you calculate efficiency?

Answer 34

output energy(J)/Input energy(J) *100

Output divided by Input multiplied by a hundred

Question 35

What are kilowatt hours?

Answer 35

Also known as Kilojoules, they are a bigger unit of measure than Joules.

Question 36

What is energy dissipation (why is the outcome energy always smaller)

Answer 36

Lost due to useless energy such as sound or friction (thermal).

Question 37

Why is it important to buy products with energy efficient designs?

Answer 37

They use less electricity.

Question 38

Ways to increase efficiency?

Answer 38

• reduce friction as much as possible
• insulate from heat loss (heat energy)
• use capacitors (formerly condensers)