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Voltage, current, resistance, and power can be calculated using ohm’s law. Below are the formulas for these calculations. At a given voltage when resistance increases, current decreases. When resistance decreases, current increases. The chart below left shows the relationship between voltage, current, and resistance. The chart below right shows the relationship between power, voltage, and current.

E = I * R

I = E / R

R = E / I

P = E * I

E = P / I

I = P / E

P =

E * I

E =

I * R

I =

P / E

R =

E / I

120 Volt 60 Watt Light Bulb Circuit

12 Volt 60 Watt Light Bulb Circuit

Voltage (E) and power (W) are known, how to calculate current (I).

Voltage (E) and current (I) are known, how to calculate resistance (R).

Voltage (E) and power (W) are known, how to calculate current (I).