SL Paper 3
The circuit shown may be used to measure the internal resistance of a cell.
The ammeter used in the experiment in (b) is an analogue meter. The student takes measurements without checking for a “zero error” on the ammeter.
An ammeter and a voltmeter are connected in the circuit. Label the ammeter with the letter A and the voltmeter with the letter V.
In one experiment a student obtains the following graph showing the variation with current I of the potential difference V across the cell.
Using the graph, determine the best estimate of the internal resistance of the cell.
State what is meant by a zero error.
After taking measurements the student observes that the ammeter has a positive zero error. Explain what effect, if any, this zero error will have on the calculated value of the internal resistance in (b).
An electrical circuit is used during an experiment to measure the current I in a variable resistor of resistance R. The emf of the cell is e and the cell has an internal resistance r.
A graph shows the variation of \(\frac{1}{I}\) with R.
Show that the gradient of the graph is equal to \(\frac{1}{e}\).
State the value of the intercept on the R axis.