A non-ideal battery with internal resistance r is connected as shown to a collec

Question

A non-ideal battery with internal resistance r is connected as shown to a collection of eight identical light bulbs, each with the same resistance R. Known values: epsilon = 120 V r = 0.01 ohm R = 3.00 ohm a. Rank the brightness of the bulbs, from brightest to dimmest. b. Suppose that bulb I could be exchanged for a new variety of bulb that is identical to the original in every respect except that its filament is 25% longer and 25% thicker (greater diameter). By what percentage would DeltaV((the voltage difference across bulb 1) change? c. Referring to the original circuit (as shown above): You are now offered a choice of removing either the straight wire A or the straight wire B. Which action would result in a larger change in the total current supplied by the batter)' (and what kind of change -an increase or a decrease)? Be sure to show all work and calculations for each alternative.

Explanation / Answer

a) all bulb are short circuited except 1,2,4

so brightness order is 1>2=4>3=5=6=7=8

b) total resistance initially = 3 + 3/2 + 0.01 = 4.51 ohm => current = 120/4.51 => V1 = 360/4.51 = 79.82 V

total resitance finally = 3/1.25 + 1.5 + 0.01 = 3.91 ohm => current = 120/3.91 => V1 = 360/(1.25 x 3.91) = 73.66V

% difference = (79.82-73.66) x 100/79.82 = 7.717 % decrease

c) if removed A,

total resistance = 18/11 R + 0.01 = 4.919 ohm

if removed B,

total resistance = 27/14 R + 0.01 = 5.796 ohm

so more change in removing B

in both cases current will decrease

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