Electrical Systems Exam 1

AGM 4600 Exam 1 Material (9/9/2026)

Voltage (V)

The electrical PRESSURE that pushes charge through a circuit.

Current (I)

The movement of electric charge.

Volts (V)

Measurement of Voltage

Amperes (amps)

Measurement of current

Resistance (R)

The opposition to current flow.

Ohm’s Law Equation

V = I * R

Required Parts for Basic Electrical Circuits

Voltage Source, Conducting Path, Load, Closed Path for Current Flow.

Conventional Flow

Defined historically as a positive charge moving from positive to negative. How many diagrams show the direction of flow.

Electron Flow

Electrons move away from the negative terminal and are drawn toward the positive terminal. Actual motion of electrons.

Why does filament in a lightbulb glow?

Resistance that limits current and creates extreme heat.

A Basic Circuit (Series) Drawing

Parallel Circuit Drawing

Series-Parallel Drawing

Equation to Calculate Total Resistance in Series

R_t = R₁ + R₂ + R₃ + …

Equation to Calculate Total Resistance in Parallel

1/R_t = 1/R₁ + 1/R₂ + 1/R₃ + …

Current Equation for Parallel Circuits

I_t = I₁ + I₂ + I₃ + …

Reducing Series-Parallel Circuit

1) Find the parallel section.

2) Replace it with one resistor.

3) Add the series resistance.

Kirchhoff’s Current Law

At any point in a circuit, the total current entering equals the total current leaving.

Kirchhoff’s Voltage Law

The algebraic sum of all the potential differences in a closed loop is equal to zero.

Power

The rate of doing work.

Energy

Power multiplied by time.

Watts (W)

The measurement of Power

Watt-Hours (Wh) or Kilowatt-Hours (kWh)

The measurement for energy.

Formula for Power

P = V * I

Formula for Energy

E = P * t

What does a power rating mean?

How much power a resistor or load can safely dissipate.

Electric Charge

A property that can move through conductors.

Direct Current (DC)

Voltage stays constant in polarity. (ex. batteries)

Alternating Current (AC)

Direction of voltage reverses repeatedly. (ex. Utility power systems)

Single Phase Power

One repeating AC waveform supplies the load. Common in homes and light commercial spaces.

Three-Phase Power

Three AC waveforms are offset by 120 electrical degrees. Common in commercial and industrial facilities.

Service Entrance

Conductors and equipment from the utility connection to the service equipment.

Service Equipment

Equipment at the service point that includes the first disconnecting means.

Meter Base

The location where the utility measures electrical energy used by the building.

Panelboard

The enclosure that holds breakers and distributes power to branch circuits.

Feeder

Conductors between the service equipment and another panel or disconnect.

Branch Circuit

Conductors from a panel to lights, receptacles, or equipment loads.

Circuit Breaker

Opens automatically when current stays too high for too long or when a fault occurs. Can be reset.

Fuse

Melts open once the current exceeds its limit. Must be replaced.

Ground Fault Current Interrupter (GFCI)

Compares hot and neutral current. When the difference is large enough, it opens the circuit to reduce shock risk.

Arc Fault Circuit Interrupters (AFCI)

Constantly monitors the electrical current and waveform patterns on a circuit. When it detects a spark, it instantly trips to cut power and prevent electrical fires.

Outlet

Any point where power is provided to a load, device, or receptacle.

Receptacle

The part of an outlet that accepts a plug.

Branch Circuit

Conductors that run from the panel to outlets and loads.

Service Equipment

The first disconnecting means for the building service.

Feeder

Conductors that carry power from service equipment to another panel.

Panelboard

The cabinet that holds breakers and distributes power to circuits.