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Then they both use the same amount of amps, when plugged in the same voltage/Hz outlet? But the lumens would be different? 67.165.185.178 ( talk) 05:23, 25 November 2022 (UTC).
Okay, I just Google'd "are LED light bulbs ohmic?" and the 1st response was "LEDs are not Ohmic materials, meaning the relationship between current and voltage is not linear." So back to my older question on how do LED light bulbs work with the same voltage as incandescent bulbs.
67.165.185.178 (
talk)
01:46, 26 November 2022 (UTC).
Neither incandescent nor LED lamps are "ohmic" if that means having constant resistance R so that Ohm's law quoted by Lambian exactly applies. An incandescent lamp has a positive temperature coefficient of resistance. The high inrush current to a cold lamp (e.g. R = 40 ohms) causes the tungsten filament to heat and the current to reduce in milliseconds to a stable illumination value e.g. I = 0.86 RMS amp, V = 120 RMS VAC, R = 140 ohms, P = 103 watt. A constant-voltage mains supply is suitable for an individual lamp. In equipment where many vacuum tube (valve) filaments are connected in series, direct connection to a mains supply can cause uneven overheating during switch-on so this is avoided by adding a negative-temperature-coefficient thermistor to the series circuit. LEDs have a steeply rising exponential current/voltage characteristic so LED lamps that contain them include a driver circuit that converts the alternating current from the mains to an effectively constant-current through the LED(s) - often this is achieved by switching the LED(s) on/off with variable duty cycle at an imperceptible high frequency. Philvoids ( talk) 15:46, 26 November 2022 (UTC)
Science desk | ||
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< November 24 | << Oct | November | Dec >> | Current desk > |
Welcome to the Wikipedia Science Reference Desk Archives |
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The page you are currently viewing is a transcluded archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages. |
Then they both use the same amount of amps, when plugged in the same voltage/Hz outlet? But the lumens would be different? 67.165.185.178 ( talk) 05:23, 25 November 2022 (UTC).
Okay, I just Google'd "are LED light bulbs ohmic?" and the 1st response was "LEDs are not Ohmic materials, meaning the relationship between current and voltage is not linear." So back to my older question on how do LED light bulbs work with the same voltage as incandescent bulbs.
67.165.185.178 (
talk)
01:46, 26 November 2022 (UTC).
Neither incandescent nor LED lamps are "ohmic" if that means having constant resistance R so that Ohm's law quoted by Lambian exactly applies. An incandescent lamp has a positive temperature coefficient of resistance. The high inrush current to a cold lamp (e.g. R = 40 ohms) causes the tungsten filament to heat and the current to reduce in milliseconds to a stable illumination value e.g. I = 0.86 RMS amp, V = 120 RMS VAC, R = 140 ohms, P = 103 watt. A constant-voltage mains supply is suitable for an individual lamp. In equipment where many vacuum tube (valve) filaments are connected in series, direct connection to a mains supply can cause uneven overheating during switch-on so this is avoided by adding a negative-temperature-coefficient thermistor to the series circuit. LEDs have a steeply rising exponential current/voltage characteristic so LED lamps that contain them include a driver circuit that converts the alternating current from the mains to an effectively constant-current through the LED(s) - often this is achieved by switching the LED(s) on/off with variable duty cycle at an imperceptible high frequency. Philvoids ( talk) 15:46, 26 November 2022 (UTC)