Principles of ElectricityPrinciples of Electricity

Background to electricity, circuits, Background to electricity, circuits, and how to calculateand how to calculate

Parts of the AtomParts of the Atom Electrons – negatively charged particles that Electrons – negatively charged particles that

revolve around the nucleus of the atom.revolve around the nucleus of the atom. Protons – Positively charged particles that Protons – Positively charged particles that

revolve around the nucleus of the atom.revolve around the nucleus of the atom. Neutrons – No charge in the atom.Neutrons – No charge in the atom.

-These parts are important to know -These parts are important to know because they determine the charge of the atom.because they determine the charge of the atom.

-The charge of the atom creates the -The charge of the atom creates the energy used as electricity.energy used as electricity.

Parts of a CircuitParts of a CircuitConsists of 4 PartsConsists of 4 Parts

- Source- Source- Conductors- Conductors- The Load- The Load-Control Device-Control Device

1 - Source1 - SourceSource – Produces the force that causes Source – Produces the force that causes

electrons to move.electrons to move.Think of a water source that pushes water Think of a water source that pushes water

through a pipe. Same principle.through a pipe. Same principle.Electrons (-) are attracted by positive Electrons (-) are attracted by positive

charges, and repelled by negative charges, and repelled by negative charges. (Opposite charges attract each charges. (Opposite charges attract each other.)other.)

2 - Conductor or Path2 - Conductor or PathConductors – Provide an easy path for Conductors – Provide an easy path for

electrons to move throughout the circuit.electrons to move throughout the circuit.Copper is the most commonly used Copper is the most commonly used

conductor in electronics and residential conductor in electronics and residential wiring.wiring.

Other conductors include other metals, Other conductors include other metals, and water.and water.

3 - Load3 - LoadLoad – Part of the circuit that changes the Load – Part of the circuit that changes the

energy of the moving electrons into energy of the moving electrons into another form of useful energy.another form of useful energy.

Think of a light bulb as a load. Think of a light bulb as a load. As electrons move though the filament of As electrons move though the filament of

the lamp, the energy of electrons in motion the lamp, the energy of electrons in motion is changed into heat and light energy.is changed into heat and light energy.

4 - Control Device4 - Control Device Control Device – Opens or closes the circuit for Control Device – Opens or closes the circuit for

electrons to flow.electrons to flow. A light switch is a great example. The lights are A light switch is a great example. The lights are

off, electrons can’t flow through to complete the off, electrons can’t flow through to complete the circuit because the switch is open. When the circuit because the switch is open. When the switch is closed, the electrons can flow, and the switch is closed, the electrons can flow, and the circuit is closed.circuit is closed.

Switches can be classified as NO (normally Switches can be classified as NO (normally open) or NC (Normally closed)open) or NC (Normally closed)

Four Values to Measure ElectricityFour Values to Measure Electricity

VoltageVoltageAmperageAmperageResistanceResistanceWattsWatts

VoltageVoltageThe force that moves electrons is call The force that moves electrons is call

VOLTAGE.VOLTAGE.The unit to measure voltage is known as The unit to measure voltage is known as

volts.volts.The common voltage a residential circuit is The common voltage a residential circuit is

120 volts.120 volts.When calculating formulas, voltage is When calculating formulas, voltage is

labeled as “E”.labeled as “E”.

CurrentCurrentCurrent – Movement of electrons.Current – Movement of electrons.Current is measured in Amperes or amps.Current is measured in Amperes or amps.A typical residential circuit measures 15 A typical residential circuit measures 15

Amps.Amps.The specifications for a common The specifications for a common

residential circuit are 120V/15Aresidential circuit are 120V/15AWhen calculating formulas, current is When calculating formulas, current is

labeled as “I”.labeled as “I”.

ResistanceResistanceThe opposing force in electrical current.The opposing force in electrical current.When electrons flow through a conductor, When electrons flow through a conductor,

the are opposed by an insulator. The the are opposed by an insulator. The insulator provides resistance.insulator provides resistance.

Coating on a wire is the insulator.Coating on a wire is the insulator.Unit of resistance is the OHM.Unit of resistance is the OHM.OHM’s law states - Voltage / Current = OHM’s law states - Voltage / Current =

ResistanceResistance

Ohm’s Law Cont.Ohm’s Law Cont.Voltage (E), Current (I), Resistance (R)Voltage (E), Current (I), Resistance (R)Problem – We need to find the resistance Problem – We need to find the resistance

of a 120V/15Amp Circuit.of a 120V/15Amp Circuit.What’s the formula?What’s the formula?E / I = RE / I = RAnswer? 8 OhmsAnswer? 8 Ohms

Power and Watts LawPower and Watts LawPower is the time rate of doing workPower is the time rate of doing workDefined in two ways: The rate at which Defined in two ways: The rate at which

electric energy is delivered to a circuitelectric energy is delivered to a circuitThe rate at which an electrical circuit uses The rate at which an electrical circuit uses

electrical energy, or how much work it can electrical energy, or how much work it can do.do.

Watts Cont.Watts Cont.Most electrical equipment is rated based Most electrical equipment is rated based

upon watts usedupon watts usedFor example a light bulb may be rated at For example a light bulb may be rated at

60w, 100w, and so on60w, 100w, and so onAmount of electricity your dwelling uses is Amount of electricity your dwelling uses is

measured in kilowatt/hours used.measured in kilowatt/hours used.Power formula – P = E x I.Power formula – P = E x I.Volts times current equals watts.Volts times current equals watts.

Kilowatt HoursKilowatt HoursMeasures how much electricity your Measures how much electricity your

dwelling usesdwelling usesFormula – KWH = Power x Hours /1000 Formula – KWH = Power x Hours /1000

Times rate in $Times rate in $Example – 1200w X 2hrs / 1000 (kilo Example – 1200w X 2hrs / 1000 (kilo

means 1000) x .10$means 1000) x .10$Cost = .24$Cost = .24$

3 Kinds of Circuits3 Kinds of CircuitsSeriesSeriesParallelParallelSeries – Parallel Series – Parallel

Series CircuitsSeries CircuitsElectrical circuit that only has one path for Electrical circuit that only has one path for

electrons to flow.electrons to flow.Open Loop – the circuit is not complete. Open Loop – the circuit is not complete. In simple terms, the switch is open, not In simple terms, the switch is open, not

allowing electrons to flow to the load to allowing electrons to flow to the load to complete the circuit.complete the circuit.

Voltage DropVoltage DropVoltage Drop – if there are two or more Voltage Drop – if there are two or more

loads in the circuit, the volts are distributed loads in the circuit, the volts are distributed among the loads evenly.among the loads evenly.

The total voltage in each load would equal The total voltage in each load would equal the source.the source.

Example – Two lights are wired in the Example – Two lights are wired in the same 120V circuit. The voltage in each same 120V circuit. The voltage in each load will be 60V. Add the two together, load will be 60V. Add the two together, =120V. =120V.

Parallel CircuitsParallel Circuits The loads are connected between the two The loads are connected between the two

conductors that lead to the energy source.conductors that lead to the energy source. There is no voltage drop if two or more loads There is no voltage drop if two or more loads

are connected in parallel.are connected in parallel. Example – A vanity light that has three lights. Example – A vanity light that has three lights.

If wired in parallel, the voltage at all three If wired in parallel, the voltage at all three loads is 120V, same as the source.loads is 120V, same as the source.

If wired in series each light bulb would If wired in series each light bulb would produce only 40 volts eachproduce only 40 volts each

Series ParallelSeries ParallelLoads operate independently.Loads operate independently.Meaning one switch to a light can be Meaning one switch to a light can be

turned off, but another can still operate.turned off, but another can still operate.Example of a parallel circuit – In your Example of a parallel circuit – In your

kitchen, you might have 3 different lights. kitchen, you might have 3 different lights. Each has their own switch. However, they Each has their own switch. However, they are connected on the same line, at the are connected on the same line, at the breaker box. Hence, there are different breaker box. Hence, there are different lines going to each load from the sourcelines going to each load from the source

SafetySafetyNever work in the circuit while it’s plugged Never work in the circuit while it’s plugged

in. Always disconnect the lead from the in. Always disconnect the lead from the source.source.

Before powering up the circuit, make sure Before powering up the circuit, make sure all wires are properly connected. all wires are properly connected.

Never run the circuit with an exposed wire.Never run the circuit with an exposed wire.

Safety Cont.Safety Cont.Never touch an exposed wire while Never touch an exposed wire while

connected. connected. Never allow exposed wires touch. It Never allow exposed wires touch. It

creates a short.creates a short. If you are unsure if you are allowed to plug If you are unsure if you are allowed to plug

in the circuit, ask me.in the circuit, ask me. If an emergency occurs, get my attention If an emergency occurs, get my attention

immediately.immediately.