LED Strip Light addition -- battery power?
I am wanting to install the LED strip lights under my awning as an upgrade. I am looking at the set that comes with remote, so I can turn on/off & dim the lights. The set is from Amazon http://www.a...
Forum Discussion
RandACampin wrote:tenbear wrote:RandACampin wrote:
Current is the same in the entire circuit...therefore a fuse anywhere in the circuit will afford the same protection.
"The current is the same in the entire circuit."
That is true in normal operation, but if a short develops in the wire, the current will be very high between the battery and the short. The fuse will only protect the circuit if it is located between the short and the battery. Shorts can happen anywhere that the wire rubs against something, especially the metal frame.
And the fuse will protect it no matter where it is in the circuit. Car fuse panels are nowhere near the battery, RV fuse blocks are often at the other end of the trailer from the battery on the tongue.
Ohms law means that no matter where the short is the current is the same throughout the entire circuit whether the short is at or near the battery the entire conductor (circuit) will see the same rise in current.
I think you're thinking more of Kirchhoff's current law and its corollaries. For a simple loop, the current through any portion of it will be equal (in a DC analysis, at least). Once there's a short, the circuit is no longer a simple loop, but has two sections in parallel, and the current is not equal throughout the circuit.
If the short happens before the fuse, the fuse is not a part of that leg of the circuit, and it does not serve to limit the current by blowing out, and so very bad things happen. (RV circuits may well have many parallel segments by design, too; if there are multiple lights on one circuit, they're wired in parallel, and the current through each light is independent of the others.)
Car fuse panels are fed by one (or possibly more) heavier wires, that go to bigger fuses or fusible links close to the battery. Similarly, on my RV, there's a self-resetting circuit breaker near the battery and a heavy wire from it to the main DC fuse panel, some distance away. The circuit breaker is sized such that it will provide sufficient protection for the heavy wire (it won't let too much current flow so that the wire gets too hot), even though it would be more than the branch circuits could safely handle. The branch circuits from the fuse panel then have their individual fuses, suitably sized for their requirements.
