Yes, Ohms law applies in light bulbs.
Instead of a linear graph you get a curve because of the changing resistance.As
the voltage increases the current increase becomes smaller and smaller.Since it
is not linear the change in current slows down as the voltage increases.Still,
at low voltage you have low current and at high voltage you have high current
as I said.
From: Lee Hart <[email protected]>
To: Paul Dove <[email protected]>; Electric Vehicle Discussion List
<[email protected]>
Sent: Thursday, November 5, 2015 11:01 AM
Subject: Re: [EVDL] Suitable Load?
Paul Dove via EV wrote:
> Halogen bulbs are made in general for 6V, 12V, 24V... Using too low
> a voltage will produce little current and too high a voltage will
> produce high current and overheating of the filament
Actually, light bulbs don't behave like resistors. Ohm's law doesn't
apply. :-)
A light bulb's apparent resistance changes drastically with temperature.
The cold resistance (measured with an ohmmeter) is easily 1:10th that of
its hot resistance (current divided by voltage at full rated voltage).
Depending on the type of light, an 8-1 change in voltage only causes
about a 2:1 change in current.
This means that light bulbs can be used as crude constant-current loads.
The current only changes slightly despite large changes in voltage. This
characteristic is ideal for testing batteries, where you'd like the
current to stay the same despite changes in cell or battery voltage.
--
Any intelligent fool can make things bigger, more complex, and more
violent. It takes a touch of genius, and a lot of courage, to move
in the opposite direction. -- Albert Einstein
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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