Every electrical system must have three parts: source, load, and circuit.

Everything resists electricity to some extent. This resistance is measured in Ohms (an ohm is a unit of measurement for resistance, reactance or impedance). Ohms are typically represented by the Greek letter “Omega”;	Everything resists electricity to some extent, even copper wire. This resistance is what makes the load work.
Ohm’s law dictates: As voltage increases, current increases As resistance increases, current decreases. The amount of electrical energy consumed is measured in watts.	It forces the electricity to make something happen (light a bulb, run a motor, etc.) in order to get through to the positive charge. Everything we use electricity for converts the electrical energy into mechanical energy, light or heat.

Materials that offer low resistance to electrical flow are called “conductors”. Metals (copper, gold, silver, aluminum), wool and water and good conductors.

Materials that have a high resistance to electrical flow are called “Insulators”. Examples include glass, plastic, rubber, air and wood.

Again, everything resists electricity to some extent. If you use a single “AAA” battery connected to a 5 mile copper wire attached to a flashlight bulb; the bulb will be dim if visible at all. On the other end; even insulators will bow to the power of electricity if there’s enough power behind the charge – example: lightning going through the air!

The Power Formula

The “Power formula” is used to determine how much power will be consumed by an electrical circuit. In the United States, the power formula is well known as the “West Virginia” formula.

The Power Formula
W=VA (or W = V * A)
W = power in Watts
V = voltage in Volts
A = current in Amperes

Note: The Universal Ohm’s Law used the abbreviations
E=Voltage,
I=Amperage,
P=Wattage,
R=Resistance
Internationally known as "Pie"

American Theatre Standards

Gauge of wire	10	12	14	16	18
Capacity in Amps	25	20	15	6	3
Capactiy in watts	3k 3,000	2.4k 2,400	1,800	720	360
(K = Kilowatt / 1,000 watts)

Dimmer:	1.2k	2.4k	3k	4k	6k
Amp usage (& fuse)	10	20	25	35	50
Dimmer Safety: The amp rating for a dimmer is what the rating for the dimmer’s fuse or circuit breaker should be.

Fuses and Circuit Breakers are designed to prevent overloads or short-circuits from happening.

A fuse works by a meltdown of a sensitive wire inside the fuse holding.

If too much power tries to go through the fuse, this wire “burns out” before your equipment does. Once a fuse is used, it must be replaced – it cannot be repaired.

Fuses come in an array of shapes, sizes and sensativities.

A circuit breaker works by using some of the extra power to trigger a switch which breaks the circuit.

If an overload or short-circuit does occur, a great deal of heat is emitted at the breakdown point, and the results can be both dangerous and/or expensive.

By knowing the American Theatre / Electric Standards, you can be sure to practice safe habits when working with dimmers and cable. You can also determine what size fuse you need to replace the one which burnt out on opening night.