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Experiment to investigate the relationship between the resistance of a light dependent

resistor (LDR) and its distance from a light source.

(a) (i) Connect the circuit as shown below. The LDR is xed at the closed end of a tube.

(ii) The lamp is taped to the half metre rule. Light the lamp b! closing the switch.

(b)"entl! insert the half metre rule inside the tube. #hen the half metre rule can no

longer move$ the lamp is in contact with the LDR. The distance between the lamp and the

LDR is %.% cm. Record the ammeter and voltmeter readings. Calculate the resistance R of

the LDR.

& ' ...................................

' ..................................

R ' ..................................

(c)(i) Remove the half metre rule out of the tube b! a few centimetres and record new

values for &$ and d.

(ii) Repeat part (c)(i) until a total of six sets of readings of d$ & and is obtained. &nclude

in !our table of results values for R$ lg R and lg d.

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(d)(i) lot a graph of lg R( ! axis) against lg d (x axis).

(ii) Draw the line of best t.

(iii) Determine the gradient and the !*intercept of this line of best t.

"radient ' .................................

+ intercept ' ..............................

(e) &t is suggested that the resistance R of the LDR and the distance d between the

LDR and the light source are related b! the e,uation

R = adb

where a and b are constants.

-se !our answers to (d)(iii) to determine values of a and b. "ive appropriate units$ where

applicable.

(f) state an! sources of errors and diculties that !ou encountered during carr!ing out

the practical. /uggest possible improvements.

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