How to convert Volts to Ohms

How to convert electrical voltage in volts (V) to electric resistance in ohms (Ω).

It is possible to calculate ohms from volts and watts or amps, but you cannot convert volts to ohms since volt and ohms units do not measure the same quantity.


Volts to ohms calculation with amps

The power P is equal to the voltage V times the current I:

P = V * I

The current I is equal to the voltage V divided by the resistance R (ohm's law)

I = V / R

Therefore the power P is equal to:

P = V * V / R = V2 / R

Therefore the resistance R in ohms (Ω) is equal to the square value of voltage V in volts (V) divided by the power P in watts (W):

R(Ω) = V2(V) / P(W)

Therefore ohms are equal to the square value of volts divided by watts:

Ohms = Volts2 / Watts

or

Ω = V2 / w

Example

Find the resistance in ohms of a resistor given a voltage of 5 volts and a power of 2 watts.

The resistance R is equal to the square of 5 volts divided by 2 watts which is equal to 12.5 ohms.

R = (5V)2 / 2W = 12.5Ω

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