Final answer:
To determine a battery's internal resistance, measure voltage across a known resistor and the current through the circuit. Calculate the emf of the battery and use the voltage drop due to internal resistance to find the internal resistance.
Step-by-step explanation:
To determine the internal resistance of a battery, you can conduct a simple experiment with a known external resistance (R), the battery in question, and measurement devices such as a voltmeter and an ammeter. The steps are as follows:
- Connect the battery in series with the known resistor.
- Measure the voltage across the resistor (VR) using the voltmeter.
- Measure the current (I) through the circuit using the ammeter.
- Calculate the circuit's total voltage drop (VT). As you know the voltage drop across the resistor (VR), you can determine the battery's emf (E) when there is no current flow (open-circuit).
Apply Ohm's Law (VR = I x R) to find the voltage across the resistor. The difference between the emf (E) and VR when current flows gives you the voltage drop caused by the internal resistance of the battery (Vint). Then, use Vint = I x r (where r is the internal resistance) to calculate the internal resistance of the battery. This method assumes the battery's internal resistance remains constant for the range of currents measured.