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Apr 19 2013 09:56pm
Quote (drxscillator @ Apr 19 2013 11:37pm)
That principle applies for any resistance of R, although you're right that analogy was not that great. Think of closing the switch as adding another path for current to flow, when you add another path for current to flow the total current produced by the emf increases and due to ohm's law when current increases resistance must decrease in order to maintain a constant voltage.


yea i know but i thought the emf produces a fixed current, like say 8Amps or w/e. and if u add another current than u gotta take away more amps from it =\
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Apr 19 2013 10:19pm
Quote (FamilyGuyViewer @ Apr 19 2013 10:56pm)
yea i know but i thought the emf produces a fixed current, like say 8Amps or w/e. and if u add another current than u gotta take away more amps from it =\


emfs aren't a current source. It creates a potential rise = potential drop (I*R) of the circuit. The higher resistance of the circuit the less current will be in the circuit. Think of it as trying to push object through a thick, viscous liquid such as oil. If you exert a steady push (emf), you can move a small object at a high speed (small R, large I) or a large object at a low speed (high R, small I)
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Apr 19 2013 10:46pm
Quote (drxscillator @ Apr 20 2013 12:19am)
emfs aren't a current source. It creates a potential rise = potential drop (I*R) of the circuit. The higher resistance of the circuit the less current will be in the circuit. Think of it as trying to push object through a thick, viscous liquid such as oil.  If you exert a steady push (emf), you can move a small object at a high speed (small R, large I) or a large object at a low speed (high R, small I)


o ok, do u mind summing it up again? 3 pages to look back =\
and my first part for first question is correct?
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Apr 20 2013 10:32am
Quote (FamilyGuyViewer @ Apr 19 2013 11:46pm)
o ok, do u mind summing it up again? 3 pages to look back =\
and my first part for first question is correct?


First part is right.

Power absorbed = I²R
For part two when you close the switch the equivalent resistance of the circuit decreases and total current increases(Itotal = Ib + Icde). A and B will become brighter because of the increase of current but C and D will become dimmer because the current Icde is now being split between three bulbs instead of two
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Apr 20 2013 10:52am
Quote (drxscillator @ Apr 20 2013 12:32pm)
First part is right.

Power absorbed = I²R
For part two when you close the switch the equivalent resistance of the circuit decreases and total current increases(Itotal = Ib + Icde).  A and B will become brighter because of the increase of current but C and D will become dimmer because the current Icde is now being split between three bulbs instead of two


kk thanks, why not use the other power equation? P = IV?
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Apr 20 2013 11:10am
Quote (FamilyGuyViewer @ Apr 20 2013 11:52am)
kk thanks, why not use the other power equation? P = IV?


I always use it for showing the power balance on multi-loop circuit problems
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Apr 20 2013 11:50am
VI = I^2R
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Apr 20 2013 11:55am
Quote (hasuchObe @ Apr 20 2013 01:50pm)
VI = I^2R


wat lol
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Apr 20 2013 11:57am
Quote (FamilyGuyViewer @ Apr 20 2013 12:55pm)
wat lol


just like he said, they are equivalent.
what does V = ?
V = IR

now plug IR in for V in the power equation

P = VI = (IR)I = (I^2)R
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Apr 20 2013 12:14pm
Quote (drxscillator @ Apr 20 2013 12:32pm)
First part is right.

Power absorbed = I²R
For part two when you close the switch the equivalent resistance of the circuit decreases and total current increases(Itotal = Ib + Icde).  A and B will become brighter because of the increase of current but C and D will become dimmer because the current Icde is now being split between three bulbs instead of two


how do i explaint he first part using ohms law..
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