Voltage and Current

Voltage is the electric force that causes the free electrons to move from one atom to another.

Just like water needs pressure to force it through a hose, electrical current needs some force to make it flow. A volt is the measure of electric pressure. Voltage is usually supplied by a battery or a generator.

The scientific symbol for voltage is the letter "E" dating back to the early days of electricity when it was called "Electromotive Force." Electricians and wiring books use the letter "V", for Volts.

Current is electricity in motion. It measures the amount of electrons that can flow through a material like a conductor. Electrical current is measured in amperes or "amps" for short. Amperes is like the amount of water flowing through a hose in a certain amount of time or the amount of electricity flowing through a wire. The scientific symbol for amps is the letter "I".

When current flows through a conductor it creates heat because of resistance. Resistance is how tight the material is holding the electrons. You may notice that a cord from an appliance may feel warm after running for a long time. That is the amperage flowing in the circuit. The more amps moving the more heat is produced. When a wire carries too many amps for its size, it becomes "overloaded" and the insulation can melt and cause a fire or can shock you if you touch it. That's why it is important to have the correct wire size. For example, use a heavy enough extension cord so it doesn't get real warm when you use it.

Smaller and shorter wires have more resistance than wider and longer wires because the current has a "tighter" space to move through.

The measurement of resistance is called ohms, and the scientific symbol is the letter "R".