Physics Equations for Electrical Power

  • #1
I'm in year 11, doing Physics for GCSE and my actual ending GCSE is on Friday which Is where I finish school.

I'm 16 and in the UK, I need help with the following equations:
P = I^2 x R (why is this equation used)
- all the power equations
- How to calculate uncertainty

<< Mentor Note -- OP has edited this post to correct the equation. See Russ' quote below for the original equation that Russ is replying about >>
Last edited by a moderator:

Answers and Replies

  • #4
I meant power sorry
No prob - just have a look at the link, se if it gives you what you need snd let us know if you have any follow-ups.
  • #5
Science Advisor
Homework Helper
Gold Member
I'm sitting in my car waiting for my twins to finish their GCSE physics exam so this is a bit late but....

First think about _where_ the power is being dissipated.

If we are talking about the power dissipated in a resistor then I and V refer to the current and voltage through and across the resistor.

If you are talking about the power delivered by a battery then I and V apply to the battery.

In some cases you only know one variable (I or V) so you can use..

And ohm's law

To make either...


Then which you use depends on which variable you know.

One of my son's has just called to say the exam was "ok but challenging". How did you find it?