Register to reply 
Why does bulbs glow bright in parallel? 
Share this thread: 
#1
Sep1313, 12:08 PM

PF Gold
P: 1,467

I have searched google and got no satisfying answer.Someone said that the overall resistance is less so as the voltage is same,the current increases.I don't think this is correct because the current for a single bulb is reduced.Can you give a satisfying answer?



#2
Sep1313, 12:21 PM

P: 178

two bulbs connected in parallel would have significantly lower resistance even if the current has to be divided upon them , consider each one of 15 ohms and a voltage of 30 volts
if they were connected in series , total resistance would be 30 ohms and so intensity will be 1 amp while if the bulb was connected in parallel , the total resistance would be 7.5 ohms , total intensity will be 4 amps divided by 2 for each lamp , 2 amps for each lamp ! the intensity is divided , but also the resistance has hugely been reduced 


#3
Sep1313, 12:28 PM

P: 62

Consider a source of potential difference 'V' and two bulbs of equal resistance 'R'.When they are connected in series the current through them is 'V/2R'.When they are connected in parallel the NET current is '2V/R' and the current through EACH of the bulbs is 'V/R'.So basically the splitting of current doesn't decrease the current through the bulbs by a larger value.



#4
Sep1313, 12:35 PM

P: 1,290

Why does bulbs glow bright in parallel?
The brightness of a bulb is related to the power transformed .Power =V^{2}/R.
Consider two bulbs having resistances R each connected across a battery having voltage V. 1)When in Series  The equivalent resistance is 2R .Hence P_{1}=V^{2}/2R 2)When in Parallel  The equivalent resistance is R/2 .Hence P_{2}=2V^{2}/R Clearly P_{2}>P_{1} 


#5
Sep1313, 09:19 PM

Sci Advisor
HW Helper
Thanks
PF Gold
P: 5,064




#6
Sep1413, 01:50 AM

HW Helper
Thanks
P: 5,165

The brightness of any particular bulb is determined by the voltage across that bulb. (A) If you have a pair of identical bulbs, and power them in parallel from a 12V battery each bulb will glow with a certain brightness. (B) If you connect those bulbs in series and power the combination from a 24V battery each will glow with a brightness identical to that in part (A). Because each bulb still "sees" 12V across it then the current is identical with that in part (A). 


#7
Sep1413, 02:03 AM

HW Helper
P: 7,048




#8
Sep1413, 02:59 AM

P: 1,074

Say we have two 110VAC bulbs, each in a box with its own brightness meter and a switch and an adequate voltage source that can power both bulbs.
Turn on 1 bulb, its meter has a reading. Turn on the other bulb, its meter reads the same. The first meter does not change when you turn on the second bulb (no interaction). Each bulb puts out X lumens when connected to 110V. Connecting 2,3,4,5,6 bulbs in parallel does not change the 110V so each bulb behaves as if the others are not there. If the 110V is "not adequate" then there could be interactions. Like your house lights dimming when the air conditioning is turned on. 


Register to reply 
Related Discussions  
Three Bulbs in a Circuit, two parallel, one series.  Introductory Physics Homework  2  
Light Bulbs in Series vs. Parallel  Introductory Physics Homework  2  
Light bulbs in parallel and series  Introductory Physics Homework  2  
65W bulbs connected in parallel... (hopefully easy)  Introductory Physics Homework  4  
Light Bulbs in a parallel circuit  Introductory Physics Homework  3 