# Electromagnetic coil and capacitors vs resistance

I'm not really sure if this is even scientific but while calculating how much energy is stored in electromagnetic coils and capacitors, pretty much the same formula is used:
For electromagnetic coils it's U=0.5LI2
For capacitors it's U=0.5CV2
Why I think they're the same is that in a sense L to coils is sort of the same as C to capacitors. Same goes for V and I
The formula used for resistance is pretty much the same( well resistance doesn't store energy, uses it) with a slight difference which is there's no 0.5
U=RI2
Why don't we have the same pattern for resistance? Are these formulas even realevant?

anorlunda
Staff Emeritus
Why would you expect them to be the same? As you said, R does not store energy. and ##RI^2## is not energy it is power. See my signature below.

• sophiecentaur
Why would you expect them to be the same? As you said, R does not store energy. and ##RI^2## is not energy it is power. See my signature below.
So energy for resistance is actually U= RIq?
But what about coils and capacitors? Are those actually the same formula adjusted for coils and capacitors? If so, what is the mother formula. Cause the conserved energy in movement shows the same pattern of K=0.5mV2 which you could say that mass to an object is sort of like L to coils and C to capacitors
Too many questions, sorry :)

anorlunda
Staff Emeritus
So energy for resistance is actually U= RIq?
a

No, the energy lost in a resistance is ##\int RI^2\, dt## Or, if the power P is constant for a time T, then energy is P times T.

For the others, just consider the similarities in form of the equations to be coincidences.

• a

No, the energy lost in a resistance is ##\int RI^2\, dt## Or, if the power P is constant for a time T, then energy is P times T.

For the others, just consider the similarities in form of the equations to be coincidences.

Ohhhh Thank you

• anorlunda