# Grade 12 Physical Science Practical Investigation Electric Circuits memo

Grade 12 Physical Science Practical Investigation Electric Circuits memo internal resistance:

### Determining the Resistance of a Battery

1. Investigative Question:

• What is the internal resistance of the battery in the circuit?Explanation: This question is asking you to find out how much resistance the battery itself provides when current flows through it. This is important because the internal resistance can affect the battery’s performance in a circuit.

2. Hypothesis:

• If we measure the voltage across the battery and the current flowing through the circuit, then we can calculate the internal resistance of the battery using Ohm’s Law.Explanation: You’re predicting that by changing the current in the circuit and measuring the corresponding voltage, you can apply Ohm’s Law (V = IR) to determine the internal resistance of the battery. The hypothesis is based on the idea that the relationship between voltage, current, and resistance will help you find the unknown value—here, the internal resistance.

3. Variables:

• Independent Variable:
• The current flowing through the circuit.
Explanation: This is what you will change during the experiment by adjusting the load (like changing the resistance) in the circuit. As you change the load, the current in the circuit will vary.
• Dependent Variable:
• The voltage across the battery.
Explanation: This is what you will measure in response to the changes in current. As the current changes, the voltage across the battery will also change, and you will record these values.
• Control Variables:
• The type of battery used, the temperature, and the equipment used to measure voltage and current.
Explanation: These are the factors you’ll keep constant to ensure a fair test. You want to make sure that only the current is changing so that the relationship between the voltage and current can accurately reflect the internal resistance of the battery. For example, using the same battery throughout the experiment ensures consistency in your results.