Physics
Physics
Problem
A 12 V battery of negligible internal resistance is connected in series with two resistors of resistances 4 Ω and 8 Ω. (i) Draw a neat labelled circuit diagram showing the correct position of a voltmeter that will read the potential difference across the 8 Ω resistor. (ii) Calculate the current flowing through the circuit. (iii) Calculate the reading shown by the voltmeter.Intuitive explanation
When resistors are in series, they share the same current, but the voltage divides among them based on their resistance—larger resistors "use up" more voltage. To find what the voltmeter reads across the 8 Ω resistor, first calculate the total current using Ohm's law with the total resistance, then apply Ohm's law again to just that one resistor. The voltmeter must be connected in parallel across only the 8 Ω resistor to measure its individual voltage drop.
Intuitive explanation
When resistors are in series, they share the same current, but the voltage divides among them based on their resistance—larger resistors "use up" more voltage. To find what the voltmeter reads across the 8 Ω resistor, first calculate the total current using Ohm's law with the total resistance, then apply Ohm's law again to just that one resistor. The voltmeter must be connected in parallel across only the 8 Ω resistor to measure its individual voltage drop.