Electrical Principles & Technologies Topic 3 Flashcards
Energy
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
Chemical Energy
Energy stored in chemicals
Potential energy
Released when chemicals react
Electrical Energy
The energy of charged particles
Electrons are negatively charged
Electrical energy is transferred when electrons
travel from place to place
Mechanical Energy
Energy of movement or energy of the potential to move
Ex. Throwing a baseball
Thermal Energy
Heat energy
Total kinetic energy of the particles in a substance
The faster the particles move more kinetic energy
Energy Transformation
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
Input Energy
Refers to the amount of energy put into a device
Output Energy
Refers to the amount of energy that comes out.
Electromagnetic Induction:
Generation of electric current in a conductor by a changing magnetic field.
Usable energy:
Refers to the energy that a device can effectively convert into a desired form of energy to perform useful work.
Wasted energy:
Refers to energy that’s not effectively converted into the desired form of energy & is therefore not useful for performing the intended task.
Oersted’s Law
States that electric currents create a magnetic field
Created by Hans Christian Oersted was a Danish physicist and chemist.
Power
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
Energy
The Formula
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)
Percent Efficiency (% Efficiency)
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
Thermocouple
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
Energy Dissipation
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
Parts of the motor:
Commutator, Armature, Electromagnet, Permanent magnet, & metal brushes
Commutator
A split ring that breaks the flow of electricity for a moment and then reverses the connection of the coil
Armature:
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.
Electromagnet
Made by swapping current carrying wire around a metal core ( usually soft iron core). It becomes a magnet when current flows through the wire.
Permanent magnet
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
Metal Brushes
Mechanism that makes electrical contact with the moving commutator in a motor.
Used to reverse the flow of electricity through the electromagnetic coil
Transformers
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
Alternating Current
The current that flows back and forth 60 times per second
* Symbol: AC
Devices that use it: electricity in household circuits
Direct Current
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!
EnerGuide Labels
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
Increasing Efficiency
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
Faraday’s device
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!
