LX 2: Basic Electrical Concepts and Wiring
To use electricity, we need to know about it. Not just for safety reasons, but also because we need to know if our rig suits the venue/s.
Electricity: When electrons move from one atom to another (http://www.energyquest.ca.gov/story/chapter02.html)
- Electrons have a negative charge
- Protons have a positive charge
- Neutrons are neutral
- The nucleus is the centre
Electron drift: The average speed a particle moves along a conductor, it can’t travel at a consistent speed because it bumps into other particles (http://www.s-cool.co.uk/a-level/physics/current-charge-and-voltage/revise-it/drift-velocity)
Voltage/Electromotive Force (EMF): Potential Difference
Voltage in UK: 230/240V
Voltage in USA: 120V
But it can change so be careful. Voltage increases could blow fuses.
In UK it used to be 240V but it changed to 230V. However it’s expensive to change so old theatres can still use 240V, but new theatres must use 230V.
Current: Flow of electrons in a complete circuit making a transfer of energy
It’s measured in Amperes (Amps) and is written as I
- Resistance: Opposition to the flow of electrons.
- It increases with heat and cable length
- The smaller the cable = The more resistance
- It likes open space where it’s cool or it gets hot and angry
- The hotter it gets, the hotter everything else gets, which means more resistance which makes it hotter
It’s written as Omega
This is Ohms law.
- If we know the Current and Resistance then I x R = V
- If we know the Voltage and Resistance then V divided by R = I
- If we know the Voltage and Current then V divided by I = R
How to Wire a Plug
- Get a wire and a plug
- Unscrew plug
- Measure the wire against the plug to see how much coloured wire you need
- Cut the rubber bit of the wire leaving the coloured bits, so the coloured bits can go into the plug. Don’t have too much or too little
- Use wire cutters to cut the ends of the coloured wires to see the copper. Hold onto the coloured wires and not the rubber, because if you hold the rubber, you may end up pulling the coloured wires out even more, and end up with too much.
- Inside the plug, loosen the three screws slightly
- Put the wire inside the plug.
- Blue is neutral so it goes under the left screw, making sure the screw touches the copper. Then tighten the screw, but not too much or too little.
- Yellow/Green is Earth so it goes under the top screw, making sure the screw touches the copper. Then tighten the screw, but not too much or too little.
- Brown is Live so it goes under the left screw, making sure the screw touches the copper. Then tighten the screw, but not too much or too little.
- Put the cord clamp on , make sure you don’t trap the wires.
- Look at the fuse. For up to 700w you use a 3A fuse. For 700W – 1200W you use a 5A fuse. For 1200 and above you use a 13A fuse. Check the sticker/plate with the maximum power consumption
- Double check the wires are in the right places.
- Put the outside of the plug on.
Stuff to remember
- When I tried it, I made the mistake in 5,
- It may help to twist the copper wires so they fit
- If there are just two wires, then it’s double insulated. It’s like normal except without the Earth wire. Make sure the Earth wire isn’t loose though.
The cable grip is the cord clamp.