This document defines key electrical concepts and principles: - Electricity is the flow of electrons through conductors driven by voltage, which is analogous to water pressure. Resistance impedes current like friction impedes water flow. - Ohm's law states that current is directly proportional to voltage and inversely proportional to resistance. It defines the relationship between voltage, current, and resistance in a circuit. - Power is calculated by multiplying voltage by current and measured in watts. Energy relationships can also be determined from power calculations in a circuit. - Circuits are either open, preventing current from flowing, or closed, allowing current. A fuse acts to open a circuit if too much current flows.

2.  Identify and describe the scientific principles
related to electricity.
 Describe electrical terminology.
 Define Ohm’s law.
 Explain electrical power and energy
relationships.

3.  All matter is made
up of atoms.
 Atoms are made up
of:
› Electrons
› Protons
› Neutrons
Each element has its own unique structure.

4.  Atoms
› Nucleus
 Protons: positive charge
 Neutrons: neutral charge
› Orbits
 Electrons: negative
charges circle the nucleus
in orbits
Neutrons
Electricity is the flow of electrons
from atom to atom in a conductor.

5.  An electrical generator
(or battery) forces
electrons to move from
atom to atom.
 This push or force is like
the pressure created by a
pump in a water system.
 In an electrical circuit this
pressure (electromotive
force) is called voltage.
 The volt (V) is the unit by
which electrical pressure
is measured.

6.  Opposition to flow in electrical circuits is called
resistance (or impedance).
 Measured in Ohms by using an ohmmeter.
 One ohm, or R is the amount of electrical
resistance overcome by one volt to cause one
amp of current to flow.
 Electrical current follows the path of least
resistance.
 Electricity can encounter resistance by the type
of conductor, the size of conductor and even
corrosion on the connections.

7. Water flowing through a hose is a good
way to imagine electricity Water is like
Electrons in a wire (flowing electrons
are called Current)
Pressure is the force pushing water
through a hose – Voltage is the force
pushing electrons through a wire
Friction against the holes walls slows
the flow of water – Resistance is an
impediment that slows the flow of
electrons
.
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5.2 Concepts of Current, Voltage, Conductor, Insulator, Resistance Current

8. 8
The Open Circuit
The open circuit is a very basic circuit that we should all be
very familiar with. It is the circuit in which no current flows
because there is an open in the circuit that does not allow
current to flow. A good example is a light switch. When the
light is turned off, the switch creates an opening in the
circuit, and current can no longer flow.
You probably figured that since there are "open circuits" that there are probably also "closed
circuits". Well, a closed circuit is when the switch is closed and current is allowed to flow
through the circuit.
A fuse is a device that is used to create an open circuit when too much current is flowing.
5.3 Concepts of Energy & Power, Open & Short Circuits

9. Power calculations
› The unit used to describe electrical
power is the Watt.
› The formula: Power (P) equals voltage
(E) multiplied by current (I).
P = I x E
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10.  Power calculations (cont)
› How much power is represented by a voltage of 13.8 volts
DC and a current of 10 amperes.
 P = I x E P = 10 x 13.8 = 138 watts
› How much power is being used in a circuit when the
voltage is 120 volts DC and the current is 2.5 amperes.
 P = I x E P = 2.5 x 120 = 300 watts
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11.  Power calculations (cont)
› You can you determine how many watts are being drawn
[consumed] by your transceiver when you are transmitting
by measuring the DC voltage at the transceiver and
multiplying by the current drawn when you transmit.
› How many amperes is flowing in a circuit when the
applied voltage is 120 volts DC and the load is 1200 watts.
 I = P/E I = 1200/120 = 10 amperes.
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12. Multimeters will measure
Voltage, Current and
Resistance.
Be sure it is set properly to
read what is being
measured.
If it is set to the ohms
setting and voltage is
measured the meter could
be damaged!