Electrical circuits have basic components like switches, loads, hot and neutral wires. Voltage is electrical pressure that can be alternating current (AC) or direct current (DC), while current is the flow of electrons measured in amps. Resistance is a component's opposition to current flow and is measured in ohms. Common electrical measurements include voltage, current, resistance, frequency, and temperature. Digital multimeters are typically used to measure these components and ensure circuits are functioning properly.

1. Electrical Basics
Test & Measure

2. Basic Electricity
Basic components of an electrical circuit.
Switch
LoadGround
Hot
Neutral

3. What is AC & DC
• “AC” stands for Alternating Current “DC”
stands for Direct Current
• AC is denoted by the the words “AC” or the
symbol
• DC is denoted by the words “DC” or the
symbol
• The majority of applications are AC
Ohm’s Law
V = I x R
volts = amps x resistance
Electricity is made up of voltage, current,
and resistance.
Using the analogy of water
flowing through a hose:
Voltage is the pressure at the ends of the hose.
Current is the water flowing through the hose.
Resistance is the diameter of the hose (wire).
Basic Electricity

4. Typical Measurements
• Current
– 1 amp is equal to 1000 milliamps
– 1 amp is equal to 1,000,000 micro
amps
– 1 milliamp is equal to .001 amps
– 1 micro amp is equal to .000001 amps
• Milli is depicted as a lower case m in front
of the symbol
– i.e. mA or mV
• Micro is depicted as a µ in front of the
symbol
– i.e. µA or µV
Symbols
Basic Electricity
V – Voltage
A – Current (in amps)
Ω
Hz
NCV
F°/C°
– Resistance (in ohms)
– Frequency
– Non-Contact Voltage
– Temperature
– AC Voltage
– DC Voltage
– Capacitance
– Continuity
– AC & DC Voltage
– Diode Check

5. • Voltage is the amount of electrical force (pressure) it takes to push
current (electrons) through an electrical conductor (wire).
• Voltage can be either “AC” or “DC”. (Alternating Current or Direct Current)
• Voltage is what is typically measured at an outlet or electrical box.
Typical Testers Used For Detecting or Measuring Voltage
Dual Lead Probes
Non-Contact
Probes
V = I x R
Volts = amps x resistance
Digital MultimetersSolenoid Tester
Typical Application
An appliance or piece of equipment is
not working or an end-user wants to
install a new wiring device so they
want to find out if voltage is present.
What is Voltage?

6. V AC Voltage
Typical application types:
• Household Outlets, Switches, Doorbells, panels, circuit breakers
• Heating elements, Security Systems
Check for energized circuits and verify proper voltage in typical home applications.
Why? Incorrect voltage can cause improper operation or premature failure of electrical
devices. For example, a home that has a voltage of 137 volts may burn out ceiling fan
motor. Alternately, too little voltage can cause failure as well.
Symbols

7. Typical application types:
• Automotive Testing
• DC Motor Controls
• Batteries
Check for proper voltage in automotive and industrial circuits. DC is found more in
industrial applications than residential.
Why? Incorrect voltage can cause improper operation or premature failure of electrical
devices. Just as with AC Voltage, too much or too little voltage can cause heating issues
within motors and other electric components.
DC VoltageV
Symbols

8. • Current is the amount of electrons flowing through a circuit.
(1 Ampere = 6.5 billion-billion electrons-per-second flowing through a wire)
• The measurement of current is stated in “Amps” or “milli-Amps
(mA)” (1000th of an amp).
• Current can be either “AC” or “DC”. (Alternating Current or Direct Current)
• Current is typically measured with a clamp meter
Typical Tester Used For Measuring Current
V = I x R
Volts = amps x resistance
Digital Clamp Meter
Typical Application
A circuit breaker keeps on tripping so
an end user wants to find out the
amount of amps being used by an
appliance, light fixture or piece of
equipment.
What is Current?

9. Typical application types:
• Circuit Board Testing
• Power Supplies; In-Rush Current
• Circuit Breaker Panels
Verify that the current draw does not exceed the maximum value of the component.
Why? Too much current can cause heating issues that will reduce the life of electric and
electronic components. For example, an incorrectly wired fan motor’s life may be
reduced by 50% if there is too much current draw.
AC/DC CurrentA
Symbols

10. • Resistance is the amount of “friction” in a wire or circuit.
• Resistance is stated in Ohms
• Resistance is most commonly measured using a multimeter set to
the Ohms position
• Continuity is a circuit with very low resistance and this is typically
tested with a continuity tester or digital multimeter.
(a wire that has a break in it does not have continuity)
Typical Testers Used For Measuring Resistance / Continuity
Continuity Tester
Digital Multimeters
V = I x R
Volts = amps x resistance
Voltage/Continuity
Testers
Typical Application
A user wants to test if a fuse is blown
or if a power cord is good and does
not have a break in it.
What is Resistance?

11. Ω Resistance
Typical application types:
• Ground Circuits
• Resistor Value Verification
• Circuit Board Testing
Check the resistance values of outlet grounds or resistors found on circuit boards.
Measurement is in Ohms.
Why? Too much resistance may cause stray current to find another path to ground. For
example, a receptacle ground wire incorrectly connected may cause excess heating in the
ground wire.
Symbols

12. Typical application types:
• Switches, Outlets, Extension Cords, fuses, and heating coils
• Unenergized Low Voltage Wiring
Check for a continuous circuit.
Why? Verify the status of fuses, extension cords, and other types of wiring. For example,
landscaping lighting is typically buried around gardens. Digging may actually cut a wire,
rendering the circuit useless.
Continuity
Symbols

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