# Is Ohm's Law applicable for only DC or for both?

Usama Khurram
Is ohm's law (V=IR) works for both AC and DC. PLz explain in details

Also let me know which formula is right for power calculation for AC and DC circuits. (P=VI or P=VICos)

## Answers and Replies

proton007007
ohms law is valid for both ac and dc . but the v=ir form is not actually the ohms law . this form is only valid for dc .
in AC we use the actual expression ..
J=sigma*E
J is current density
sigma is conductivity
E is electrif field

for dc p=vi=v^2/r=i^2*r can be used
the other one mentioned by you is for ac.

proton007007

cabraham
dc: V = I*R, R = resistance
ac: V = I*Z, where Z = R + jX, X = reactance, Z = impedance

Claude

davenn