# Fundamentals of Electric Circuits

## Electrical Circuits

Welcome to this video lesson on *electrical circuits.*

An electrical circuit is __a closed path on which electrons flow from a voltage source__. The point at which the electrons enter the circuit is referred to as the “source” of electrons, or the power source.

When we talk about the flow of electrons through a circuit, it is referred to as the flow of current in a circuit. Current always flows from positive to negative in terms of direction in a circuit. A good way to think about this is to imagine a river. If the water in a river is the electrons, then the current of the river would be the equivalent of the current flow of power for electricity. Like a river always flows toward sea-level, electricity, or current, always flows from positively charged terminals to negatively charged terminals.

From this diagram we can see a representation of a circuit flow. We see that the current flows from the positive terminal of the voltage source through the load on the circuit back to the negative source. Now we have not talked about loads yet but in the simplest of terms an electrical load can be thought of as anything that causes resistance for the current to flow. Going back to our river analogy if we put a pillar in the middle of the river the water would have to flow around the pillar and there would be a force of resistance from the pillar on the water that would force the water around the pillar. In that regards an electrical load is anything that puts any type of resistance on the flow of current or anything that uses the power from the circuit. As a result if you put a light bulb in a circuit the light bulb is the load of the circuit because it takes power out of the circuit to turn on and thereby causes a resistance and reduction of power out of the circuit.

The last few things we need to discuss about electrical circuits is how we measure things like the *power, current, or resistance*. **Power** is measured in Voltage (V). **Voltage** is equal to Joules/Coulomb. **Joules** are a measurement of energy and the Coulomb is the standard measurement of electric charge. **Current** is measured using the Ampere. The **Ampere**, or amp whose symbol is “A”, is named after Andre-Marie Ampere, from France. The amp is defined as the 1 Coulomb/second in a given cross sectional area for the carrier of the current. The final measurement used is the **Ohm** (). The Ohm, named after German physicist Georg Simon Ohm is the name given to the unit used for measuring resistance. As it is the base unit there is no comparison to give as it relates to another unit of measurement.

I hope that helps. Thanks for watching this video lesson from Mometrix.