We’re surrounded by electrical circuits—our phones, light switches, the battery used to start a car. But most of us don’t understand what the electricity is doing to power what we’re using.

The key to understanding power is knowing the fundamentals of electricity, which are used to calculate power consumption, battery capacity, and much more.

The electricity fundamentals highlighted in this module are introduced as simply as possible for clarity; for more detailed examples or explanations, click the info icons.

### Volts

Voltage is a measurement of electromotive force in a circuit. It can be described as the amount of pressure, force, or “push”.

For example, if a circuit has a measurement (or rating) of 5 volts (V), then electricity is pushed through the line with a force of 5 V.

Why is this important? Every circuit has resistance in it. Resistance impedes the flow of electrons through a conductor. Voltage can be used to ensure that the effect of resistance is minimized.

### Amps

Amperage is a measurement of electrical current flowing through a circuit. Specifically, it is a measurement of the amount of electrons that flow through a conductor material (such as a copper wire). For example, a wire conducting electricity may have a flow measured (rated) at 5 amps (A).

Why is this important? As with voltage, amperage has a lot to do with the resistance of the circuit. Resistance in an electrical circuit impedes the flow of electrons through a conductor; therefore, every circuit conductor has a maximum flow rate assigned to it that it can safely handle.

### Watts

Wattage is a measurement of electricity generated or consumed in a circuit. There is a simple rule to remember when determining watts (W): “A watt is a watt is a watt”. **The amount of watts generated in a circuit must be equal to or greater than the watts consumed by the load.**

In relation to volts and amps, watts never change as electricity flows through an electrical circuit; they are a constant value. Watts can be generated and consumed, and they may be reflected as different amounts, but they are usually only measured at the generator and the load. What happens between the watts-generated value and the watts-consumed value is measured in volts and amps.

Visualize a water faucet above a bathtub. When you turn the faucet on all the way, the water comes out with force. If you put your hand in the the stream of water, it pounds on your skin. Think of that pressure of the water as **voltage.**

Now, turn the faucet halfway off. This reduces the amount of water flowing from the faucet. Think of that change in flow, or current, as **amperage**.

Amperage and voltage go hand-in-hand, just like the water coming out of a faucet. The higher the amperage (the greater the flow of water), the higher the voltage (the more forcefully the water stream hits your hand).

- Watts never change in a circuit.
**Watts generated must be greater than watts consumed.**

Where the watts come from is irrelevant to the load. All that matters is that enough watts are brought into the circuit to keep the appliances operating. The source of the generated watts is decided based on geographic location and available resources.

There are two commonly used types of electricity: alternating current (AC) and direct current (DC).

If your power is supplied by the utility grid or a gasoline generator, it is probably an AC circuit. If your power comes from a battery, it is likely a DC circuit.

Identifying a DC-powered appliance (load) is very easy. There are two basic criteria:

- Does it have a battery in it (disposable or rechargeable)?
- Can it run directly from a battery (such as a 12 V cigarette lighter adaptor (CLA) connection or from the NATO connection in a vehicle)?

Simply put, if the answer to either or both of these questions is yes, then it is a DC load.

Most small DC systems use 12 or 24 volts (normally expressed as 12 VDC or 24 VDC), and most AC systems in the United States use 120 or 240 volts (120 VAC or 240 VAC).