Alternating Current (AC), standard house current, is delivered to homes by the local electric utility. It reverses direction 60 times per second in a residential circuit.

Amperage describes current flow. It’s the number of electrons per second passing a given point on the wire. To calculate the number of amps flowing through a circuit, divide the total watts by the voltage: a = w 4 v

Circuits are unbroken paths along which an electrical current flows. Each circuit forms a closed loop from the power source to the load and back.

Conductors are metal wires, usually aluminum or copper, that conduct the electricity from its source to its load.

Derated Load is the computed load of a given electrical circuit or group of circuits after it has been adjusted per the formulas given in the National Electric Code (NEC.)

Direct Current (DC) flows in one direction. Batteries supply direct current.

Electricity is the flow of electrons that takes place when a charge is created, raising the voltage potential of one point over another.

Ground is the conducting connection between an electrical circuit or an electrical device and the earth.

Loads are any appliances that use electricity, from a night-light to a central air conditioner.

Ohm’s Law is the relationship between voltage, amperage, and resistance: Voltage = Amperage x Resistance.

Resistance is a measure of how well a material conducts electricity. It’s measured in ohms. Conductors have low resistance, insulators have high resistance.

Voltage is a measure of electrical pressure or force. The greater a circuit’s voltage, the more current it will deliver to a given load. Most homes have a 240-volt service. Actual voltage fluctuates from 220 to 240 (or 110 to 120 volts).

Wattage is power consumption: the product of voltage and amperage. It’s used to estimate circuit capacity.

Watt-hours is a measure of power consumption over time. One watt-hour equals one watt of electricity used for one hour.

or Subscribe to read the full Field Guide