RACK/ELECTRICAL
V=IRV=IR

Ohm's law

The electrical essentials. No guesswork.

Inputs

YOUR SYSTEM
V
0.1200
Ω
132

Result

METER
Current through load
3.00A
For the specified voltage and resistive load
Power dissipated
72.0W
Load resistance
8.0Ω
Applied voltage
24.0V
AMPLIFIER TO LOUDSPEAKERAMP+-8 ΩCURRENT THROUGH LOAD : 3.00 A
Voltage, current & resistance: Resistive load

How it works

Three quantities, one relationship.

Current is voltage divided by resistance. Multiply voltage by current to find the power being delivered to a purely resistive load.

The formula

I=VRI = \frac{V}{R}
P=V⋅I=V2RP = V \cdot I = \frac{V^2}{R}
  • II — current in amperes
  • VV — voltage in volts
  • RR — resistance in Ω\Omega

Worth knowing

At a fixed voltage, halving the resistance doubles the current and doubles the power. That extra current is why low speaker impedances can stress an amplifier.

Assumptions

For DC or AC into a purely resistive load. Reactive loads have phase shifts and require complex impedance and power factor for a complete calculation.

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