Measuring Internal Resistance of Zinc Carbon Cell: Tips & Tricks

[StaceyParker]

I'm doing an experiment to measure the internal resistance of a zinc carbon cell (battery) and have slightly confused myself! Do I use the ε= IR + Ir formula? And if so how in the world do I use it! I know that I can work out R by using V and I values but how do I find the EMF of the battery? And what value do I use for I cos I have hundreds cos current isn't a constant!
I've royally confused myself!

 

[GCT]

The emf of the battery should be listed on the battery, the internal resistance can be found either through research or it may even be indicated on the battery

$$\Delta V=EMF-IR$$

The internal resistance can be experimentally determined by hooking the battery up to the resistor,

the total V of the circuit will be $$\Delta V_{circuit}=I(R)=I(R_{eq}+R_{internal})$$

 

[Chi Meson]

The emf will be the terminal voltage when there is no current flowing. THat is, test the voltage of the battery when it is not attached to the circuit.

 

[Delta]

You could do a plot of various values of V (=IR) against the current I. As shown by the formula IR = EMF - Ir, you will see that the gradient will be -r, whilst the y intercept will be the EMF.