Current Electricity

A complete circuit

A closed circuit. A circuit doesn't work unless it is this. There must be a full connection in the circuit, from the pole and back again.

What is needed to operate most electrical devices?

A continuous flow of electrons.

Electrical Load

A device that converts electrical energy into another form of energy, (heat, light). Toaster, Hair Dryer, Lights, Stove, etc

Efficiency

A devices energy cost and environmental impact

Solar Power

A photovoltaic cell converts the energy from light to electrical energy. They are only 30% efficient in converting light to electrical energy because there is an atmosphere between the panels and the energy source (the sun). Also they can't receive energy when it is dark. Can be used to provide electricity to homes and businesses not connected to the power grid since they are a way they can create their own electricity.

Primary or Secondary Cells

A primary cell can only be used once while a secondary cell can be recharged.

Non-renewable Resources

A resource that can not be replaced as quickly as it is being used.

Energy star symbol

A symbol on some devices that shows that they meet a minimum level of efficiency.

How do batteries work?

All batteries work on a chemical reaction between the 2 terminals. As the chemical reaction occurs the negative terminal loses electrons and will slowly decrease in size, while the positive terminal will gain electrons and increase in size. When the negative metal terminal disintegrates, the cell will stop working and the battery is dead.

Short Circuit

An accidental low-resistance connection that causes excess current flow. These can cause wires to become hot and start a fire and cause the device not to work.

Which is more environmentally friendly, an electric or a hybrid car?

An electric car since it relies solely on electricity and not partially on fossil fuels like a hybrid car. However, if the electricity is produced by a renewable source then the car is even more eco-friendly.

An incomplete circuit

An open circuit.

Wind Power

As wind blows the turbine moves.

Energy in

How much energy the device requires.

Energy out

How much useful energy a device puts out to complete its task.

Calculating the cost of using an electrical device

Multiply the energy consumed in kWh by the cost per kWh: cost= power used (in kWh)x cost of electricity OR Cost= p x cost of electricity

Renewable Resources

Natural resources that are continually replenished and will not run out., can be replaced relatively quickly.

Is potential difference always fixed between two terminals?

No it depends on the components, how they are connected, the amount of resistance.

Energuide label

On all large appliances. States how much energy the appliance will use in a month or year of average use.

Calculating the efficiency of a device

Percent efficiency= Eout/Ein x 100% The higher the percentage the more efficient the device is.

Minus Terminal

Starting point of electricity.

Electrical Power

Symbol P. Measured in Watts. P=E/delta t P=VxI V=P/I I=P/V

Electrical energy consumption (for a household)

The amount of electrical energy used, usually kilowatt- hours.

How can two conductors differ?

They can differ in their resistance, their density, the number of particles, all of which will cause the electrons to flow differently through them.

Why might a bulb glow brighter right before it burns out?

This could happen because there are too many electrons flowing through the bulb which causes more friction, more heat and more light.

Why can Hydroelectric generating stations be used for both peak and base loads?

This is because can be turned on/ water pressure increased/ brought on line quickly since water is pumped into the dam when it isn't needed yet for peak load, or can be turned off quickly/ open dam for base load.

Why must Electrodes be made from different materials?

This is because they must have different electron affinities. One must lose electrons (negative terminal), and one must gain them (positive terminal).

When is E measured in W.

When time is in minutes or hours.

When is E measured in J?

When time is in seconds.

Base Load

Minimum amount of energy needed throughout the day.

Lead Storage Batteries

(Car Batteries). The electrode is a strong sulphuric acid solution. These batteries are made up of 6 "2V" batteries that are connected in series. Therefore they produce 12V.

Rechargeable Batteries

(Nickel/Cadmium AAA, AA batteries) Can produce up to 1.5 V. The positive electron is nickel and the negative is cadmium.

Electric circuit control device

-Turns the circuit on or off by opening or closing the circuit -Objects which regulate the flow of electrons within a circuit -Switches, fuses and wires -Prevents wires from overheating (when electrons flow through wire they cause friction which causes heat).

Parts of a Battery

1. Positive Terminal- Receives electrons (metal electrode) 2. Negative Terminal- Donates electrons (metal electrode) 3. Electrolyte- A fluid or paste substance that allows the electrons to pass through the battery from the negative to the positive terminal.

1 kW is equal to

1000 W

Fuel Cell

A cell that generates electricity directly from a chemical reaction with a fuel such as hydrogen. Used in electric vehicles and cell phones.

Secondary Batteries

Batteries that can be recharged many times, (ex. car batteries). These batteries allow the chemical reaction to be reversed because they are plugged into an external energy source. This source supplies electrons that now move from the positive to the negative terminal, allowing the negative electrode to increase back to its original size.

Batteries

Convert chemical energy into chemical energy. There are many different types, and they come in many shapes and sizes.

Solar Cells

Converts sunlight into electrical energy.

Calculating the cost of using an electrical device if operating time is given

Cost to operate=power used (kW)x time(h)x cost of electricity OR cost to operate=VxIx delta tx cost of electricity

What two forms does current electricity flow in ?

Direct current and Alternating current.

Total Current in a Series Circuit

Electric Current is the same in all parts of the circuit. The electrons will not change their rate of flow at any point in the circuit because they only have one path to follow.

Resistors

Electrical devices in circuits that increase resistance (slows current).

What is a battery a combination of?

Electrochemical or Voltaic cells connected in series.

Parallel Circuits

Electrons can flow along more than one path. An interruption or break in one pathway does not affect the other pathways in the circuit. Each electrical device can be off or on within the circuit.

Direct Current

Electrons flow in one direction only. This is produced by an electric cell, such as a battery to power portable electrical devices.

Alternating current

Electrons move back and forth in a circuit (ex. in our homes since the current flow back and forth at regular intervals called cycles.)

Plus Terminal

Ending point of electricity.

Total Voltage in a Series Circuit

Equal to the sum of all the voltages added together. The voltage is shared or split between the loads.

Tidal Generation

Harnessing the energy of moving water from the ocean. Tides occur twice per day at specific times and vary in different coastal areas.

Wet Cell

Has a fluid electrolyte, usually sulphuric acid. They have two metal electrodes. Electrons move from one metal through a wire to the other metal. Are not very practical. Electrolyte evaporates easily and has a tendency to leak out.

Dry Cell

Has a paste electrolyte, usually an alkaline substance like Potassium hydroxide. Dry cells are the most common type of batteries and include AAA, AA, C, D, 9V and button cell batteries. Produce up to 1.5 V. Reasons for using them include: -sealed in a metal container -portable since they won't leak -exceptionally practical (small sizes) -some can be rechargeable -longer shelf life

Coal power generation

Have the greatest environmental effect since burning coal to produce energy adds to acid rain, particulates and other emissions.

Peak Load

Highest load of energy.

Thermal Generation

Involves heating water to produce steam which is used to move a turbine. There are various ways to produce steam: Fossil Fuels (oil, coal + natural gas), Radioactive materials, biomass (plant or animal matter) + geothermal energy.

What are the types of batteries

Primary batteries and Secondary batteries and Wet cells and Dry cells.

Series Circuit

The components are arranged one after another. There is only one path along which electrons can flow. Adding one bulb will make all bulbs dimmer. If the path is interrupted, the whole circuit can not function.

Total Current in a Parallel Circuit

The current splits when you add another electrical load since it is divided between each pathway. The total is equal to the sum of the currents in each branch.

What happens to the current in a closed circuit if the resistance increases but the voltage remains constant?

The current will decrease since there is more resistance opposing the flow of the electrons.

What happens to the current in a closed circuit when the voltage increases but the resistance remains constant?

The current will increase to allow the extra electrons to flow through the circuit.

Electrical Resistance

The degree to which a substance opposes the flow of electric currents.SI unit is ohms. Measured using an ohmeter. The greater the ohms the slower the current.

Phantom Load

The energy consumed by an electrical device when it is turned off.

Potential Difference/Voltage

The energy that each electron has and the potential difference between two points. Electrons from an outlet have more energy than those from a battery. Electrons have electric potential energy at the negative terminal of a battery. The SI unit used to measure this is the volt (v). Measured using a voltmeter connected in parallel with a load or energy source.

Electric Circuit

The flow of electrons from one place to another in a controlled path.

Electric current

The measure of the rate at which electrons travel past a certain point in the circuit at each second. SI unit is the ampere (A). Measured using an Ammeter which is connected in series with a load and always set to the highest setting.

Electrical Energy

The rate at which electrical energy is produce or consumed in a given time. Measured in watts (W). 1w=1J/s. Symbol is E.

Gauge

The thickness of a wire. The lower the number the thicker the wire. The lower the gauge the more electricity can flow through it.

Delta t

The time interval.

Total Resistance in a Series Circuit

The total is equal to the sum of all the individual resistances. As more loads are added the resistance increases.

Total Resistance in a Parallel Circuit

The total resistance is smaller than the smallest resistance. Formula is 1/Rt= 1/R1+1/R2..... When you add another electrical load the resistance decreases.

Hydro-Electric Generation

Uses fast moving water of a waterfall, river, or the water stored in a reservoir behind a dam. There 180 of these in Ontario. Have the least environmental effect since there are no heat transformations to damage the environment (natural ones have even less)

Ohm's Law calculations

V=IxR R=V/I I=V/R

Total Voltage in a Parallel Circuit

Voltage never changes, adding more paths doesn't reduce energy, only draws more current which allows the electrons to travel through.

Source of electrical energy

Wall outlets, batteries (electrochemical cells), portable generators, motors, etc. Gives a constant supply of electrons or electrical energy.

Connectors (conductors)

Wires that allow electrons to move from one place to another.

Are some circuits a combination of series and parallel?

Yes, this is an important safety features because it is necessary to electricity off in part or all of the home.

Why should you not use extra volts to power a cell?

You shouldn't do this because this could cause damage the circuit since the voltage is too much for the circuit to handle.