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Collaboration, Voice & AV · Foundational

Ohm's Law

The electrical relationship V = I x R, with power P = V x I, used to calculate voltage, current, resistance and power.

Definition

In AV work, Ohm's law and the power formula help size amplifiers, calculate loudspeaker loads, determine cable loss and plan circuits. Related forms include P = I squared times R and P = V squared divided by R. Impedance in AC circuits extends the concept of resistance.

Example

A 100 W load at 120 V draws about 0.83 A, so twelve such devices need about 10 A of circuit capacity.

Exam tip

Expect simple calculations: rearrange V = IR and P = VI to solve for the missing value.

Related terms