Why does bulbs glow bright in parallel?

In summary, the overall resistance in a parallel circuit is lower than in a series circuit, resulting in an increase in current. However, the current through each individual bulb remains the same, as the voltage is constant. Therefore, connecting bulbs in parallel will result in a brighter overall light, but the current through each bulb will not change.
  • #1
adjacent
Gold Member
1,552
63
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?:confused:
 
Physics news on Phys.org
  • #2
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
 
  • Like
Likes Zachary Siow
  • #3
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
The brightness of a bulb is related to the power transformed .Power =V2/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 P1=V2/2R

2)When in Parallel - The equivalent resistance is R/2 .Hence P2=2V2/R

Clearly P2>P1
 
  • #5
adjacent said:
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?:confused:
Because when the bulbs are connected in parallel across a voltage drop, you have the full voltage drop across each of the bulbs. When you have the bulbs connected in series, you have half the full voltage drop across each of the bulbs. So, in parallel, the current through each of the bulbs is twice as high as when they are in series.
 
  • #6
Can you give a satisfying answer?
Yours is one of those questions which is at the same time right and also wrong. http://physicsforums.bernhardtmediall.netdna-cdn.com/images/icons/icon6.gif [Broken]

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).
 
Last edited by a moderator:
  • #7
adjacent said:
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?
Assume that the power source is constant voltage, like the electricity going into your house. The power source will adjust the voltage to compensate for reduced resistance, increasing current. So with a constant voltage source, the amount of current going through each bulb in parallel is the same. Two bulbs in parallel are brighter than one bulb, three bulbs in parallel are brighter than two bulbs in parallel, ... .
 
  • #8
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.
 

1. Why do bulbs glow bright in parallel?

When bulbs are connected in parallel, each bulb has its own individual path for current to flow through. This means that the current is divided evenly among the bulbs, resulting in each bulb receiving the same amount of current and glowing with equal brightness.

2. How does connecting bulbs in parallel affect their brightness?

Connecting bulbs in parallel allows for each bulb to receive the same amount of current, resulting in them glowing with equal brightness. This is different from connecting bulbs in series, where the current is divided among the bulbs, causing them to glow with different levels of brightness.

3. Is there a limit to how many bulbs can be connected in parallel?

There is no set limit to how many bulbs can be connected in parallel. However, the more bulbs that are connected, the greater the overall current draw will be. This means that a larger power source may be needed to supply enough current for all the bulbs to glow brightly.

4. Why is it important to connect bulbs in parallel instead of series?

Connecting bulbs in parallel ensures that each bulb receives the same amount of current and glows with equal brightness. In series, the current is divided among the bulbs, causing them to glow with different levels of brightness. Additionally, if one bulb were to burn out in a series circuit, all the bulbs would go out. In parallel, if one bulb burns out, the others will still continue to glow.

5. Can bulbs connected in parallel still be dimmable?

Yes, bulbs connected in parallel can still be dimmable. The dimmer switch will control the overall amount of current flowing through the circuit, which will affect the brightness of all the bulbs in the parallel connection. Each bulb will still receive the same amount of current as the others, but the overall brightness will be controlled by the dimmer switch.

Similar threads

  • Electrical Engineering
Replies
3
Views
1K
  • Introductory Physics Homework Help
Replies
5
Views
1K
  • Introductory Physics Homework Help
Replies
6
Views
688
  • Introductory Physics Homework Help
Replies
4
Views
208
  • Introductory Physics Homework Help
Replies
4
Views
868
Replies
6
Views
1K
  • Introductory Physics Homework Help
Replies
1
Views
1K
  • Introductory Physics Homework Help
Replies
2
Views
2K
  • Introductory Physics Homework Help
Replies
2
Views
3K
  • Other Physics Topics
Replies
11
Views
11K
Back
Top