Help on physics project please.....(Internal Resistance of a Cell)?

Question

I am in higher secondary school now..i'm doing a project on Internal Resistance of a Cell and its Variation...i need some material to be added to the project..can u please tell me some useful sites where i can get the info required?..remember, remember, i am in higher secondary..so the information has to be upto the level..please!!!!!

Answer 1

First, draw an equivalent series circuit showing the cell, internal resistance, and a load resistor to help visualize the problem. You'll need a load resistor that will draw enough current from the cell to lower the voltage enough to get a meaningful measurement. Measure the voltage under load, and with no load. The difference is the voltage across the internal resistance of the cell. Try this with several resistor values. Make sure you use a high power resistor. Calculate the wattage before hooking it up.

Now, measure the voltage under load, and using Ohm's law, calculate the current through the resistor. Since this is a series circuit, the current through the load resistor is the same as the current through the cell and its internal resistance.

Now you can use Ohm's law to calculate the internal resistance of the cell. R=Voltage difference divided by the current.

The internal resistance will depend on the state of charge of the cell. Alkaline and lead-acid batteries gradually increase their internal resistance as they discharge. NiCd and NiMH cells maintain a very low internal resistance until nearly fully depleted.

Answer 2

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