SPM Questions P3: Emf Graph

SPM03/P3

The graph V agains I above shows the results of the experiment to determine the electromotive force, E, and the internal resistance, r, of a dry cell.

(a) Based on the graph in Figure 8,

(i) what happen when I increases? [1 mark]

voltage decrease

(ii) determine the value of the potential difference, V when the current, I = 0.0 A.

Show on the graph, how you determine V. [2 marks]

(enlarge the graph to see the answer)

(iii) name the physical quantity that represents the value in (a)(ii). [1 mark]

e.m.f

(b) The internal resistance, r, of the dry cell is given by

r = - m

where m is the gradient of the graph. Calculate the value of r. [3 marks]

use yr maths skill to find gradient, at the same time show the line of connected points on the graph

(c) (i) From the graph, state the value of V when I = 0.80 A. Show on the graph how you determine the value of V. [2 mark]

For this question, just show line connecting from 0.8A until touches the graph,

then state the equivalent voltage

(ii) The resistance R is given by R = V/I.

Calculate R when I = 0.80 A. [2 marks]

this is just mathematical, use whatever reading of V u've obtained from the graph from question (c)

(d) State one precaution that should be taken during this experiment. [1 mark]

- make sure all the wires are well connected with the ammeter & voltmeter

- avoid parallax error while taking the reading