Electrical Principles & Technologies Topic 3

Question 1

Energy

Answer 1

The ability to do work
oMany different kinds of energy
o Energy cannot be created or destroyed
oEnergy can be converted from one form to another
oSome energy is lost during every conversion

Question 2

Chemical Energy

Answer 2

Energy stored in chemicals
Potential energy
Released when chemicals react

Question 3

Electrical Energy

Answer 3

The energy of charged particles
Electrons are negatively charged
Electrical energy is transferred when electrons
travel from place to place

Question 4

Mechanical Energy

Answer 4

Energy of movement or energy of the potential to move
Ex. Throwing a baseball

Question 5

Thermal Energy

Answer 5

Heat energy
Total kinetic energy of the particles in a substance
The faster the particles move more kinetic energy

Question 6

Energy Transformation

Answer 6

Energy transformation: change from one form of
energy to another
Transformations happen every second of every day
Examples:
Toaster: Electrical Energy < Thermal Energy
Flashlight: Chemical Energy < Electrical, then light & thermal energy

Question 7

Input Energy

Answer 7

Refers to the amount of energy put into a device

Question 8

Output Energy

Answer 8

Refers to the amount of energy that comes out.

Question 9

Electromagnetic Induction:

Answer 9

Generation of electric current in a conductor by a changing magnetic field.

Question 10

Usable energy:

Answer 10

Refers to the energy that a device can effectively convert into a desired form of energy to perform useful work.

Question 11

Wasted energy:

Answer 11

Refers to energy that’s not effectively converted into the desired form of energy & is therefore not useful for performing the intended task.

Question 12

Oersted’s Law

Answer 12

States that electric currents create a magnetic field
Created by Hans Christian Oersted was a Danish physicist and chemist.

Question 13

Power

Answer 13

The rate a device converts energy.
Unit: Watt (W)
Equal to one joule per second
The faster a device converts energy, the higher the power rating
P = I x V
Power = Current x Voltage Watts = amperes x volts
Think back to our waterfalls: Power is equal to how high the waterfall is times how much water is going over the edge

Question 14

Energy

The Formula

Answer 14

You can use the power rating to determine the energy it uses
You multiply the rate by the length of time the device operates
Unit: Joules (J)
Time MUST be in seconds
E = P x t Energy = Power x Time
Joules = Watts x seconds
Kilowatt Hours: Devices can consume many joules in little time
Kilowatt-hour: used in energy bills, almost anytime
you’re using energy
Replace seconds with hours and watts with kilowatts (1000 watts)

Question 15

Percent Efficiency (% Efficiency)

Answer 15

The useful energy that comes out of a device, is compared to the energy that goes in.
The more energy that is converted to usable energy the more efficient it is.
Formula:
Percent efficiency: (Output energy / Input energy) x 100

Question 16

Thermocouple

Answer 16

Temperature measuring device with two conductors that are different metals
When heated they create energy
Energy Transformation:
Transforms thermal energy into electrical energy
The two metals conduct heat at different rates
Due to the difference, electricity flows from one metal to the other
Temperature affects how much electricity is produced
Good for places where a regular thermometer wouldn’t work

Question 17

Energy Dissipation

Answer 17

Law of conservation of energy: Energy cannot be created or destroyed
BUT energy coming out of a device is ALWAYS smaller than the energy put in
The “missing” or “lost” energy is usually heat

Question 18

Parts of the motor:

Answer 18

Commutator, Armature, Electromagnet, Permanent magnet, & metal brushes

Question 19

Commutator

Answer 19

A split ring that breaks the flow of electricity for a moment and then reverses the connection of the coil

Question 20

Armature:

Answer 20

Rotating shaft with a coil wrapped around it.
Its purpose is to carry current across the field, thus creating shaft torque in a rotating machine or force in a linear machine.

Question 21

Electromagnet

Answer 21

Made by swapping current carrying wire around a metal core ( usually soft iron core). It becomes a magnet when current flows through the wire.

Question 22

Permanent magnet

Answer 22

A magnet that retains its magnetic properties in the absence of an inducing field of current.
It’s purpose is used to generate a constant motor flux

Question 23

Metal Brushes

Answer 23

Mechanism that makes electrical contact with the moving commutator in a motor.
Used to reverse the flow of electricity through the electromagnetic coil

Question 24

Transformers

Answer 24

A device that changes electricity at one voltage into electricity of a different voltage
* Step-up transformer: Increases the voltage
* Step-down transformer: Decreases the voltage
Different regions have different currents supplied by the power company
* Use a transformer so you can use your North American devices
Current carrying wire wrapped around one end of an
iron core ring (primary coil)
A second current-carrying wire is wrapped around the
other side of the core (secondary coil)
* Step up: More wire on the secondary coil than the primary
* Step down: Less wire on the secondary coil than the
primary

Question 25

Alternating Current

Answer 25

The current that flows back and forth 60 times per second
* Symbol: AC
Devices that use it: electricity in household circuits

Question 26

Direct Current

Answer 26

The current flows in only one direction
* Symbol: DC
Devices that use it: Most devices that use electricity, cars, planes, light rail systems, computers, and almost anything that uses a battery.
Plug-in devices that use DC come with a power supply
* A power supply will convert the 120V AC to DC at the voltage that the device requires
* Think of the cord you plug a laptop in with!

Question 27

EnerGuide Labels

Answer 27

Large appliances sold in Canada have these labels
Tells a buyer how much energy they use in an average month or year of usage
Can compare the labels for different brands and models

Question 28

Increasing Efficiency

Answer 28

Devices from electrical to mechanical
 The worst inefficiency is friction
Devices where heat is produced
Heat lost from the system is the biggest inefficiency
 Insulate to keep heat in

Question 29

Faraday’s device

Answer 29

The device used electromagnetic forces to move an object, a hanging wire moved around a fixed magnet.
*Found a way for electricity to produce continuous motion
*Led to the electric motors we use today!

Michael Faraday demonstrated that electrical current could be generated by moving a conducting wire through a magnetic field.
* This is called Electromagnetic Induction
Through this discovery, a steady supply of large energy can be generated… A generator!