12. -15 points YF13 26 P059 My Notes Ask Your Teacher The two identical light bu

Question

12. -15 points YF13 26 P059 My Notes Ask Your Teacher The two identical light bulbs in Example 26.2 (Section 26.1) are connected in parallel to a different source, one with = 8.0 V and internal resistance 0.5 Q. Each light bulb has a resistance R 3.0 (assumed independent of the current through the bulb) (a) Find the current through each bulb. Find the potential difference across each bulb. Find the power delivered to each bulb. (b) Suppose one of the bulbs burns out, so that its filament breaks and current no longer flows through it. Find the power delivered to the remaining bulb. Does the remaining bulb glow more or less brightly after the other bulb burns out than before? O more brightly o less brightly o with the same brightness

Explanation / Answer

a)

Req = equivalent resistance of the two bulbs in parallel = R.R/(R + R) = R/2 = 3/2 = 1.5 ohm

i = current coming from the battery

i = E/(Req + r)

V = Voltage across each bulb = i Req = E Req /(Req + r) = (8) (1.5)/(1.5 + 0.5) = 6 Volts

current in each bulb is given as

i' = V/R = 6/3 = 2 A

Power delivered in each bulb is given as

P = V2/R = 62/3 = 12 Watt

b)

Req = equivalent resistance of the two bulbs in parallel = R = 3 ohm  

i = current coming from the battery

i = E/(Req + r)

V = Voltage across each bulb = i Req =  E Req /(Req + r) = (8) (3)/(3 + 0.5) = 6.86 Volts

Power delivered in each bulb is given as

P = V2/R = 6.862/3 = 15.7 Watt

more brightly

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