Fire/Arson Investigations : Fire/Arson Investigations
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One for the Engineers...
Posted by: Sir Gary (IP Logged)
Date: June 09, 2017 04:17AM
I'm a chemist, so if somebody more adept at electricity can fault my reasoning, it would be much appreciated :
These transformers are rated at 230V primary to 11.5V/3.95A secondary
(I measured the incoming voltage @ 230V on site); by my elementary calculations :
- P = IV to get the ideal current, with 50W & 12V giving an current of 4.17A;
- V=I^2R to get the bulb resistance, with 4.17A & 12V giving 0,69Ω;
- V=I^2R for the current drawn off 11.5V, giving a current of 4.08A
suggest that the ampere rating of the transformers are marginally exceeded.
These transformers are rated at 230V primary to 11.5V/3.95A secondary
(I measured the incoming voltage @ 230V on site); by my elementary calculations :
- P = IV to get the ideal current, with 50W & 12V giving an current of 4.17A;
- V=I^2R to get the bulb resistance, with 4.17A & 12V giving 0,69Ω;
- V=I^2R for the current drawn off 11.5V, giving a current of 4.08A
suggest that the ampere rating of the transformers are marginally exceeded.
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