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Ohms Law For Contractors Exam

Ohms law can be thought of as the relationship between voltage, current, and resistance

Voltage is measured in Volts (V) and is represented by the letter V

Current is measured in Amperes (A) and is represented by the letter I

Resistance is measured in Ohms (Ω) and is represented by the letter R

Current (I) = Voltage (V) / Resistance (R)
Amperes (A) = Volts (V) / Ohms (Ω)
Voltage (V) = Current (I) x Resistance (R)
Volts (V) = Amperes (A) x Ohms (Ω)

Example 1:

What's the voltage needed to generate 20 Amperes of Current in 6 ohms of Resistance?
To solve, use the formula for voltage.
V = I x R
V = 20A x 6 Ω
V = 120V

Example 2:

What is the current generated by a voltage of 120V through a resistance of 30 ohms?
To solve, use the formula for current.
I = V/R
I = 120V/30 Ω
I = 4A

Example 3:

What's the Resistance present if a voltage of 120V generates 15 Amperes of current?
To solve, use the formula for resistance.
R = V/I
R = 120V/15A
R = 8 Ω
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Written by Yanis O.

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