A straight-line graph reveals a source’s properties
The source equation has the form of a straight line. A graph of terminal voltage against current separates the e.m.f. from the internal resistance.
Follow the reasoning
- Plot terminal voltage vertically and current horizontally.
- Read the voltage intercept as e.m.f.
- Take the magnitude of the negative gradient as internal resistance.
Try it in a past paper 6
Open the question, then use its mark scheme to check your work.
Question 17
Find impulse from the area under a force–time graph.
Build the supporting skills. Practise Analysing before exploring this connection. This question has not been checked as a combined example of the connection.
Question 18
Calculate current for a cell with internal resistance.
Build the supporting skills. Practise Internal resistance before exploring this connection. This question has not been checked as a combined example of the connection.
Question 25
Interpret polarisation, transmission data and the components of a wave’s oscillation.
Build the supporting skills. Practise Analysing before exploring this connection. This question has not been checked as a combined example of the connection.
Question 8
Use LED measurements and a graph to estimate Planck’s constant and its uncertainty.
Build the supporting skills. Practise Analysing before exploring this connection. This question has not been checked as a combined example of the connection.
Show 2 more paper references
Question 17
Relate a cell’s e.m.f. to its terminal potential difference.
Build the supporting skills. Practise Internal resistance before exploring this connection. This question has not been checked as a combined example of the connection.
Question 21(a)–(b)
Relate internal resistance, current and the power delivered to a bulb.
Build the supporting skills. Practise Internal resistance before exploring this connection. This question has not been checked as a combined example of the connection.
A curated collection checked against the question papers and mark schemes; not a complete past-paper catalogue. Links open official OCR PDFs in a new tab.
Put the ideas to work
More practice is on its way
No PhysicsUK question linked yet. New eligible questions appear here as the bank grows.
Specification outcomes (4)
- 4.3.2(c)(i) Use and apply E = I(R + r) and E = V + Ir for internal resistance.
- 4.3.2(c)(ii) Use techniques and procedures to determine the internal resistance of a cell or power supply.
- 1.1.3(d)(i) Selection and labelling of axes with appropriate scales, quantities and units.
- 1.1.3(d)(ii) Measurement of gradients and intercepts from experimental results.