Solar Photovoltaic Basics, A Study Guide for the NABCEP Entry Level Exam by Sean White4324

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Electricity basics
Answer:
If W = VI and we want to solve for I then
I = W/V
I = 100W/120V
I = 0.833 Amps
Therefore, next time you go to the store, ask for a 0.833A light bulb.
If they don’t know what you are talking about, then try asking for your light
bulb in Ohms.
Since V = IR then to solve for Resistance
R = V/I
R = 120V/0.833A
R = 144 Ω
So ask for a 144 ohm light bulb.
Using W = VI and V = IR together, we can solve for W, V, I and R if we know any
two of the factors. The Ohm’s Law Wheel at the beginning of this chapter gives
derived equations to help electricians with this.
We could have looked at the Ohm’s Law wheel and seen that:
R = V 2 /P
R = 120V 2 /100W = 144 ohms
HOW TO USE A METER TO MEASURE VOLTAGE, CURRENT
AND MORE
Digital multimeters can typically measure voltage, current and resistance.
Figure 3.3 is an example of a simple and inexpensive meter that can measure
voltage, current and resistance.
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