Electricity 101

Before we start to explore what each light is and how it works, it is important that we understand how electricity itself works, how to work with it, and how to protect ourselves from it.

How electricity works

Yeah, yeah I know - you plug the light in and it works. But understanding HOW it works is extremely important when you need to create a circuit.

A circuit is the pathway of the electricity in order to power something like a light bulb or a motor (called the load).

Take a look at this video about electrical circuits and the common units and measurements we use with electricity:

Volts, Amps, and Watts Explained Links to an external site.

(Length 6:05) from the Techquickie YouTube channel

Notable things with theatre electricity

What mainly makes working with theatre electricity and lighting different than in your house really comes down to both the load and the circuit.

In a normal household or apartment light, the normal wattage of a light bulb is between 40W to 60W. In theatre, a normal incandescent stage light load is either 575W or 750W, and a moving light may require between 1000W to 2000W in order to work properly. That is a LOT of power. As a result, theatres will have many hundreds of amps of power that can be used for the lighting system only. 

As for circuits - in theatre lighting we use two types of circuits: dimming and non-dim or constant. Dimmers are devices that change the amount of voltage going through the circuit in order to alter a light's intensity. We use these with incandescent (filament) lights. A non-dim or constant circuit is always supplied with the same, constant voltage and does not dim. We use these to power moving lights and LED lights that have internal computers that regulate their intensity and all their other parameters (like pan, tilt, color mixing, etc.).

The "West Virginia" Formula

Officially called the power formula, this is a math formula that all stage lighting technicians know and will use frequently. It is used to calculate the relationship between watts, volts, and amps in an electrical circuit. If you know two of the values, you can easily calculate the third.

This formula is sometimes written as P=IxV, or power is equal to amps multiplied by voltage.

Because we prefer things to be simple and straight-forward, theatre technicians especially use a different variation of this formula:

W=VA

or watts is equal to volts multiplied by amps. This just happens to be the abbreviation for the state of West Virginia, making it even easier to remember.

Electrical Safety

Electrocution is no joke and is something that all lighting technicians need to be aware of and take every precaution possible to avoid.

It may seem obvious, but NEVER work on the wiring or components of a light while it is plugged in or turned on. Always turn it off and unplug it before you begin.

If there are any cuts or breaks in the insulation of the cable, do not use it. If the small copper conductors inside of the cable are exposed, they can create a bunch of potential safety issues especially if the copper wiring comes in contact with a person or a metal object like a batten.

Likewise, make sure that all connections between cables are secure and tight. All of the metal plugs (the prongs that stick out of the end of one side) should be fully seated into the sockets (the holes on the other side). Any gaps can cause an electrical hazard or can cause the connection to loosen itself over time and come loose.

We also rely on a concept called grounding to keep us safe. Electricity wants to return to its source as quickly and directly as possible. This includes going through a person if necessary... Interestingly enough, this return trip for the electricity is easiest for it to do through the actual ground of the Earth. So in each electrical cable there is a third pin and wire combination that, if need be, will divert electricity away from a person or damaged circuit straight into the earth so that it can return to where it came from without hurting anyone or anything. This doesn't mean you can't get electrocuted. You absolutely can. But grounding makes that much more unlikely and can save your life if something were to go wrong.