How to determine the brightness of a light bulb

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SUMMARY

The brightness of a light bulb is determined by both current and voltage, with power being the key measure of brightness. Specifically, at constant voltage, brightness can be calculated using the formula P = I²R, where P represents power, I is current, and R is resistance. If resistance decreases and current increases proportionally, the bulb will appear brighter due to the greater power output. Incandescent bulbs are not 100% efficient, meaning that a portion of power is lost as heat rather than converted to visible light.

PREREQUISITES
  • Understanding of electrical concepts such as current, voltage, and resistance.
  • Familiarity with the formula for electrical power (P = V * I).
  • Knowledge of incandescent bulb efficiency and its implications.
  • Basic grasp of how resistance affects current flow in electrical circuits.
NEXT STEPS
  • Research the efficiency ratings of different types of light bulbs, including LED and fluorescent.
  • Learn about Ohm's Law and its application in electrical circuits.
  • Explore the impact of varying resistance on current and power in practical scenarios.
  • Investigate how to measure the brightness of light bulbs using a light meter.
USEFUL FOR

Electrical engineers, physics students, and anyone interested in understanding the principles of light bulb brightness and electrical power consumption.

cy19861126
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In general, does more current/less resistance mean the brighter of the light bulb? How does voltage take into account in this case
 
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Both the current and voltage contributes to the brightness. It just depends on the configuration. If an incandescent is 100% efficient (with it isn't btw), that means all power (V*I) would be used to produce visible light rather than 90% being wasted as heat.
 
"Brightness" is a measure of power, so at constant voltage power is I^2R. If resistance is decreased and current is increased by an equal factor, the increase in current counts for more and the bulb will appear brighter
 

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