The bulbs in parallel have lower total equivalent resistance, pulling more current and lowering terminal voltage. The same could be true when connecting them to a shunt wound DC generator. Contrary to the claim in the question, the bulbs in series will burn brighter. In the case of the bulbs in series, the current I will flow through both bulbs, and the power consumed is I²R for each and 2I²R in total. Assuming equal resistance R, the bulbs will both see a current of I/2, and the dissipated power in each is I²R/4 or in total I²R/2. When the lamps are connected to a constant current source, current is indeed "divided" over the lamps in parallel. ![]() ![]() Let's first look at cases where this is not the case. This leads to more power each light bulb is getting(due to Joule-Lenz law) and brighter light bulbs. Overall, you need to increase the emf of the current source to increase the brightness of the light bulb.Ģ) As all answerers pointed it out, when we wire light bulbs in parallel instead of in series, we decrease the equivalent resistance of the circuit and therefore increase the current passing through the filaments of the light bulbs. Assuming we have an ideal conductor here, one can find that Since altering the resistance will also decrease the current passing through the light bulb and even exponentially decrease the power, we can derive a more reliable formula by using the specialized form of Ohm's law($V=IR$). However, this expression can deceive you to think that increasing the resistance of the light bulb increases the brightness. Therefore, since power is $\frac Wt$, we can derive the expression that is proportional to the power: To find which parameters we should play with to increase the power, we can use Joule-Lenz law which states that: Therefore, we should increase the power due to a current source as much as possible to increase the brightness of the light bulb. ![]() What is the term used to specify the heat energy generated by the flowing current per unit time? Power. Therefore, luminous flux is useful if we are comparing the brightness of light sources which emit light with same wavelength.įor incandescent light bulbs, brightness or luminous flux is directly related to the heat energy due to the flowing current in a conductor since these type of light bulbs are used by heating the filament until it emits visible light(assuming we have an incandescent light bulb here because other light sources like LED will have different properties). However, light sources which emit light with different wavelengths but same luminous flux can be perceived to have different brightness levels. Essentially, the brightness depends upon the luminous flux of the light source. I crafted this answer for this question in the first place but since it got closed, I will post it here to at least contribute.ġ) The brightness of a light bulb depends on various parameters, most of them being intrinsic properties of light bulbs.
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