Download Principles of Electricity

Principles of Electricity
Background to electricity, circuits,
and how to calculate
Parts of the Atom
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Electrons – negatively charged particles that
revolve around the nucleus of the atom.
Protons – Positively charged particles that
revolve around the nucleus of the atom.
Neutrons – No charge in the atom.
-These parts are important to know because
they determine the charge of the atom.
-The charge of the atom creates the energy
used as electricity.
Parts of a Circuit
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Consists of 4 Parts
- Source
- Conductors
- The Load
-Control Device
1 - Source
Source – Produces the force that causes
electrons to move.
 Think of a water source that pushes water
through a pipe. Same principle.
 Electrons (-) are attracted by positive
charges, and repelled by negative
charges. (Opposite charges attract each
other.)
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2 - Conductor or Path
Conductors – Provide an easy path for
electrons to move throughout the circuit.
 Copper is the most commonly used
conductor in electronics and residential
wiring.
 Other conductors include other metals,
and water.
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3 - Load
Load – Part of the circuit that changes the
energy of the moving electrons into
another form of useful energy.
 Think of a light bulb as a load.
 As electrons move though the filament of
the lamp, the energy of electrons in motion
is changed into heat and light energy.
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4 - Control Device
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Control Device – Opens or closes the circuit for
electrons to flow.
A light switch is a great example. The lights are
off, electrons can’t flow through to complete the
circuit because the switch is open. When the
switch is closed, the electrons can flow, and the
circuit is closed.
Switches can be classified as NO (normally
open) or NC (Normally closed)
Four Values to Measure Electricity
Voltage
 Amperage
 Resistance
 Watts
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Voltage
The force that moves electrons is call
VOLTAGE.
 The unit to measure voltage is known as
volts.
 The common voltage a residential circuit is
120 volts.
 When calculating formulas, voltage is
labeled as “E”.

Current
Current – Movement of electrons.
 Current is measured in Amperes or amps.
 A typical residential circuit measures 15
Amps.
 The specifications for a common
residential circuit are 120V/15A
 When calculating formulas, current is
labeled as “I”.
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Resistance
The opposing force in electrical current.
 When electrons flow through a conductor,
the are opposed by an insulator. The
insulator provides resistance.
 Coating on a wire is the insulator.
 Unit of resistance is the OHM.
 OHM’s law states - Voltage / Current =
Resistance
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Ohm’s Law Cont.
Voltage (E), Current (I), Resistance (R)
 Problem – We need to find the resistance
of a 120V/15Amp Circuit.
 What’s the formula?
E/I=R
 Answer? 8 Ohms
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Power and Watts Law
Power is the time rate of doing work
 Defined in two ways: The rate at which
electric energy is delivered to a circuit
 The rate at which an electrical circuit uses
electrical energy, or how much work it can
do.
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Watts Cont.
Most electrical equipment is rated based
upon watts used
 For example a light bulb may be rated at
60w, 100w, and so on
 Amount of electricity your dwelling uses is
measured in kilowatt/hours used.
 Power formula – P = E x I.
 Volts times current equals watts.
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Kilowatt Hours
Measures how much electricity your
dwelling uses
 Formula – KWH = Power x Hours /1000
Times rate in $
 Example – 1200w X 2hrs / 1000 (kilo
means 1000) x .10$
 Cost = .24$
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3 Kinds of Circuits
Series
 Parallel
 Series – Parallel
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Series Circuits
Electrical circuit that only has one path for
electrons to flow.
 Open Loop – the circuit is not complete.
 In simple terms, the switch is open, not
allowing electrons to flow to the load to
complete the circuit.
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Voltage Drop
Voltage Drop – if there are two or more
loads in the circuit, the volts are distributed
among the loads evenly.
 The total voltage in each load would equal
the source.
 Example – Two lights are wired in the
same 120V circuit. The voltage in each
load will be 60V. Add the two together,
=120V.
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Parallel Circuits
The loads are connected between the two
conductors that lead to the energy source.
 There is no voltage drop if two or more
loads are connected in parallel.
 Example – A vanity light that has three
lights. If wired in parallel, the voltage at all
three loads is 120V, same as the source.
 If wired in series each light bulb would
produce only 40 volts each
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Series Parallel
Loads operate independently.
 Meaning one switch to a light can be
turned off, but another can still operate.
 Example of a parallel circuit – In your
kitchen, you might have 3 different lights.
Each has their own switch. However, they
are connected on the same line, at the
breaker box. Hence, there are different
lines going to each load from the source
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Safety
Never work in the circuit while it’s plugged
in. Always disconnect the lead from the
source.
 Before powering up the circuit, make sure
all wires are properly connected.
 Never run the circuit with an exposed wire.
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Safety Cont.
Never touch an exposed wire while
connected.
 Never allow exposed wires touch. It
creates a short.
 If you are unsure if you are allowed to plug
in the circuit, ask me.
 If an emergency occurs, get my attention
immediately.
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