2. Let’s be real
• Electricity is obviously important information
to know
• To Lauren it’s like reading Chinese
• Use on a daily basis: absolutely, but can also
be done by memorizing the facts.
• If in doubt look it up or ask.
• SAFETY FIRST
5. If Series is used:
• Current is constant
• Voltage is divided up between all the loads. As
demonstrated the 2 40w lamps dimmed in
half.
• E.g. If there’s 12 light bulbs they would all get
1/12th of their potential.
• If one breaks the path of the current they ALL
go out.
9. Parts and Pieces
• AMPERES: current (rate of flow of electrons)
• OHMS: resistance (holding back electrons)
• VOLTAGE: potential (the difference in
electrons)
• WATTS: power (energy consumed)
10. To Know
• Electricity flows from negative to positive
• Three wires: 1. ground 2. neutral 3. hot
• Pg 36 Figure 3.14B
• Grounding is a safety for humans at the
instrument. It is sent back to its service which is
grounded. This way if we touch the instrument
we do not get electrocuted. “a short”
• Surge: an abnormal amount of amps sent thru an
existing system.
11. USE OF POWER FORMULA
• Sally goes to the store to buy a lamp, a
computer, and a flashing strobe light. She
knows that her house supplies 120 volts. The
lamp is 150 watts, the computer is 180 watts,
and the flashing strobe is 500 watts. Can she
plug all of these into a 20 amp circuit?
12. SOLUTION
• Total number of watts Sally is trying to plug in:
• 830 watts
• Formula inputs: W=VA
830 = 120 x A
830 divided by 120 = 6.9 amps
ANSWER: yes. She can plug all of this onto her 20
amp circuit.
13. Use of Ohm’s Law
• Using Sally’s information: so, Sally is using 6.9
amps of current for her disco. How much
resistance do all 3 appliances contain?
• Formula: I=E/R
– I = current (amps)
– E= voltage (volts)
– R= resistance (ohms)
15. Practical Use of Ohm’s Law
• System Designs: voltage drops over long
distances
• Mirror ball on lowest level and the designer
wanted it to go slower so create the correct
ghost load used Ohm’s law to find the correct
amount of resistance to influence the voltage.
– Think about a truck when you keep adding weight,
it has to perform more work to get up a hill
16. Understanding a light bulb
• Voltage is listed based on what type of system
they’re rated in
• The wattage is the output of light
• The resistance determines the wattage SO the
more resistance - the less wattage.
• Choosing the correct one:
– Base size
– Voltage matches voltage
– Rating of the fixture the lamp is going to be used in.
17. Cables and Connectors
• Cable Gauges
– Rated for a certain amount of current
– The cable insulation is rated for a voltage and
temperature range
– Dictates what we can plug in with those cables.
– In theatre we use 12 gauge SO or S. It is rated for
20 amps
18. types of wires
• Stranded wire
• Solid wire
• Extension cords: in theatre usually called
“jumper”
• Multi cable
19. Permanent wiring
• Music halls: because of the acoustic panels
and other details the units are hard wired into
the system and only focus/color can be
changed.
• LIMITED OPPORTUNITIES
20. Spidering
• The way we circuit shows here at RTT.
• The dimmers are in place, the circuits are run
to the grid permanently, we then use the
jumpers to connect the instruments to the
circuits.
21. Looming
• Done on touring
• Laying all of the cable together and then
bundling so that the receptacle for each
instrument is placed at the instrument.
• Can all be coiled back up together and moved
to the next location to be laid out again.
• Sometimes this is done here for cyc lights
upstage
