Edexcel A-Level Physics EMF and Internal Resistance

Practise Edexcel A-Level Physics electromotive force and internal resistance using terminal voltage, lost volts, graph intercepts and current calculations.

Exam points

use E = I(R + r) or E = V + Ir to include internal resistance in cell circuits
explain lower terminal voltage using internal resistance, lost volts or connection resistance
interpret V-I graphs by taking EMF from y-intercept and r from negative gradient

[Maximum number: 3]

'Resistivity paper' is paper covered with a thin layer of carbon.
The distance between the ends of a piece of resistivity paper is 12.0 cm . The resistivity paper is 4.2 cm wide as shown.

Figure for Question 2.4.77 - E.m.f. and internal resistance question 1 — Edexcel A-Level Physics AS

The resistance between the ends of the resistivity paper is $8.8 \Omega$ .

A student connected the ends of the resistivity paper to a cell of e.m.f. 1.5 V and a voltmeter, as shown.

The reading on the voltmeter was 1.4 V .

Calculate the internal resistance of the cell.

Internal resistance =

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2.4.77 - E.m.f. and internal resistance question 1