Ohm's Law for Alternating Currents

play

frequency (Hz)

voltage (volts)

resistance (Ω)

In an alternating current, the direction of the electric current reverses periodically, so that electrons oscillate inside the conductor at a frequency measured in number of cycles per second (or hertz, Hz). This Demonstration assumes there are no inductors or capacitors and that the impedance of the circuit is equal to the resistance of the incandescent light bulb. Then Ohm's law for the alternating current is given by

V(t)=RI(t)

, where

V

is the voltage,

R

is the resistance, and

I

is the current. The power of the circuit is

P=

V

RMS

I

RMS

or

P=

2

V

RMS

R

, where

V

RMS

is the root mean square value of the oscillating voltage, equal to

V

max



2

≈.707

V

max

, and likewise for

I

. Power is measured in ampere-volts or watts (W).