Can somebody explain internal resistance and the equations please?

My teacher didnt explain to us properly about internal resistance in circuits and I dont know how to apply the equations in order to answer circuit questions related to internal resistance. Please can somebody help me. Just to let you know I am doing OCR AS PHYSICS A spec. thanks.

Posted Wed 6th March, 2013 @ 20:56 by Former Member

glad i could help. :)

Answered Sat 9th March, 2013 @ 18:06 by Tilly - Team GR

I'm doing edexcel, but i assume it's pretty much the same.

Internal resistance is resistance within a battery (or emf source).

The equation I think you are reffering to  E = Ir + IR

E = emf, I = current, r = internal resistance and R = resistance in the rest of the circuit.

So it is basically saying that emf (voltage produced by the battery) is equal to the potential difference in the circuit + the voltage supplied to the internal resistance.

Ir = voltage supplied to the internal resistance.

IR = potential difference in the rest of the circuit.

So you add these together you get the total voltage in the circuit which is supplied by the battery - this is the emf.

Answered Sat 9th March, 2013 @ 15:59 by Tilly - Team GR

Thank You very much :D

You have been a great help!

Its not as complicated as I initially thought.

Answered Sat 9th March, 2013 @ 17:59 by Former Member