Hey guys, this is actually a question from my roommate's homework. She gave her response and I figured I'd check it over. I have some questions too!
Consider the following statement made by a physics 480 student while pondering the fact that two bulbs connected in series are dimmer than the bulb in a single bulb circuit. "A battery always produces the same amount of current. It's the same battery, so the current has to be the same. The brightness of the bulbs in a two bulb circuit changes because the bulbs are sharing that current 50-50." Do you agree or disagree with this statement? Justify your response.
The Attempt at a Solution
"In a two bulb series circuit the two bulbs are less bright than a single circuit bulb because the two bulbs must share the energy, therefore creating less flow. In a double bulb circuit the current is less than that of a single bulb because it must be shared. In a parallel circuit the flow throughout the circuit increases or is greater because of the set up and the transfer throughout goes more smooth. The current is split amongst the two devices in different paths 50-50. The brightness of the two bulbs will remain the same." -Alexa
"A battery always produces the same amount of current."
Incorrect. Power is conserved, and even that changes. The load determines current drawn from a battery. This is why the remaining bulb in a two-bulb series circuit will get brighter if you've removed one of them. You just cut your load in half! Just think of a light bulb filament as a resistor. That's really what it is, right? Assuming source voltage is constant, a decrease in resistance = increase in coulombs/second through the load, and thus a brighter light bulb, hence E=IR.
And in the case of a two-bulb parallel circuit? This is where I need your guys' help. It's counterintuitive because you'd think that removing a "resistor" would give you the same results as before. But the brightness of the remaining bulb doesn't increase. Heck, it stays the same. Is it easier to go the other way with it and start adding light bulbs in parallel? How would you explain that the total resistance of the system is decreasing and therefore the current drawn is increasing ...without giving the impression that a greater increase in current will always equate to a brighter light bulb? It's easy to see that the voltage across each light bulb is equi...
Oh, and she mentioned they have yet to cover Ohm's Law, so I'm shooting for an explanation that doesn't require it:/
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