[ELECTRON] Power / current in a lamp

[Seb Bacon]

Thanks Clive, that's *really* useful.

While I know all the equations, I'm still struggling to relate them to
the casual language used (e.g. "draws" current, "rated" voltage).  By
analogy to the lamp:

On 11 May 2010 20:16, Clive Mitchell <bigclive1 at googlemail.com> wrote:
> The 0.3A (300mA) is the current drawn at the rated voltage and the
> 3.5W is the total power dissipated, part of it being light and part of
> it being heat.

...would it be correct to say that a 12k resistor "draws" 1mA of
current at 12V?  Could the inscription on my lamp, "0.3A, 3.5W"
meaningfully be paralleled with an inscription on a resistor that says
"1mA, 0.012W"?  What do you call that inscription -- is that also a
type of rating?  Would it be equivalent to say that a typical 0.25W
12k resistor ("5mA, 0.25W") is rated at 55V? (Or something similar)?

Why do we talk about a lamp in terms of a "rated" voltage, but we talk
about resistors in terms of a power "rating"?

A 0.25W resistor will blow out somewhere above 0.25W; can I know when
the lamp we're discussing would blow from the information I've given?
Is that what "rated" voltage means, somehow?

Is the only difference in how we talk about them that the "work" we're
interested in with a resistor is its resistance at any current up to
its maximum, and the lamp its power at a given voltage?  Why are we
presumed to care about the lamp's power (rather than, say, its
lumens)?

Phew, so many questions. Thanks again!

Seb

> On 11 May 2010 17:33, Seb Bacon <seb.bacon at gmail.com> wrote:
>> On our wee lamps, it says 0.3mA, 3.5W.  What does that mean?  That the
>> lamp performs most efficiently at that current and power?