Power Loss over 1st Light Bulb in DC Circuit w/10Ω, 12Ω, 10Ω & 12V

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SUMMARY

The discussion focuses on calculating the power loss over the first light bulb in a DC circuit consisting of resistances of 10Ω, 12Ω, and 10Ω, powered by a 12V source. Participants confirm the use of Ohm's Law (V=RI) and the power formulas (P=VI and P=V²/R) to determine the current and power loss. The total resistance is calculated as 32Ω, leading to a current of 2.66A. To find the power loss specifically for the first bulb, the resistances of the two bulbs must be included in the calculations.

PREREQUISITES
  • Understanding of Ohm's Law (V=RI)
  • Knowledge of power formulas (P=VI, P=V²/R)
  • Familiarity with series circuits and total resistance calculations
  • Basic concepts of electrical resistance in materials (tungsten filament properties)
NEXT STEPS
  • Calculate the total resistance of the circuit including the light bulbs.
  • Learn how to derive current using total resistance and voltage.
  • Explore power loss calculations in series circuits.
  • Investigate the impact of filament material and dimensions on resistance.
USEFUL FOR

Electrical engineering students, hobbyists working with DC circuits, and anyone interested in understanding power loss in electrical components.

lofty28
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A DC circuit has resistances of 10Ω, 12Ω, and 10Ω respectively. Also has 2 light bulbs with identical tungsten (resistivity = 5.6* 10^-8) filament bulbs with filament thickness of 12um and length of 1.2cm. The source is a 12V.

what is the power loss over the first light bulb?


I am not entirely sure which equations to use how ever the ones which i thought to use are:
V=RI
P=VI
P=V^2 / R
I am really stuck and don't know how to find the acual power loss. I think my main issue is gather the correct information and implimenting it in the right situation.



I have attempted to find the total, R1+R2+R3= 32Ω
And then i have divided each by the source 12... 2.66A
Can someone please direct me in the right way...? I am gettin quiet frustrated with it!
 
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hi lofty28! :smile:

yes, that's the right method, find the current first, and then find the power through the bulb with that current

(but you'll need to add the resistances of the two bulbs, and add them, before finding the current :wink:)
 

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