In a laboratory experiment two identical point charges are fixed at various…

PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences

Problem

In a laboratory experiment two identical point charges are fixed at various separations in air. The measured magnitudes of the force

F

for different separations

r

are given below: •

r = 0.20\,\text{m},\; F = 1.8\,\text{N}

•

r = 0.30\,\text{m},\; F = 0.80\,\text{N}

•

r = 0.50\,\text{m},\; F = 0.29\,\text{N}

(a) Tabulate

\log_{10} r

and

\log_{10} F

for each data pair. (b) Using any two suitable points from your table, determine the slope of the

\log F

versus

\log r

graph. Show that the slope is approximately

-2

within experimental error. (c) From the result obtained in part (ii), establish the functional dependence of

F

r

in this experiment. (d) Hence calculate the magnitude of each of the identical charges used, assuming vacuum conditions throughout.