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Questions on EMF and internal resistance

Q4. A battery of e.m.f. and internal resistance r is connected in series with a variable resistor R as shown in the diagram. A voltmeter is connected as shown.

(a)

(i) State what is meant by the e.m.f of a battery.

(ii) The reading V on the voltmeter is the voltage across R.
Why is V less than ?

(3)

(b) In order to measure and r, an ammeter is used in the circuit, as shown below.

The value of R is decreased in steps and at each step the readings V and I on the voltmeter and ammeter, respectively, are recorded. These are shown in the table.

Reading on voltmeter/V
Reading on ammeter/A
4.0
0.07
3.0
0.14
2.0
0.21
1.0
0.28

 

(i) Plot a graph of V (on y axis) against I (on x axis) and draw the best straight line through the points.
(ii) Determine the values of and r from the graph, explaining your method.

(8)
(Total 11 marks)