That holds up until the thermal effects of that high current start to change the real wire's resistance. On the other hand, if you have a battery and a wire with a specified resistance, then that is merely a "high current" circuit. If you have an ideal voltage source hooked up with a wire across both sides, that is a "short circuit" because that model cannot properly describe what really happens. If you can draw and solve a circuit "properly," the line between a short circuit and a really high amperage line is very blurry.Īs others have said, there's no official line, but I find the most useful line is the point where the high-current effects in the circuit exceed the modeling of your circuit. To recap: the short circuit current is a function of several variables but is mostly determined by the nominal voltage and internal series resistance. With the values I've made up for Figure 1 you can calculate that the 9 V battery will limit the current into a dead-short to \$ I = \frac V R = \frac 9 = 480\ \text A \$. It should be clear from the model that the voltage at the battery terminals will droop with increasing current. We can usually simplify this to a simple model of an ideal voltage source and an equivalent series resistance. The short-circuit current of a battery will depend on its voltage, chemistry, size and internal structure. Simulate this circuit – Schematic created using CircuitLab The model of internal resistance is useful for this. To answer this we need to look at what limits the battery's ability to supply infinite current. ![]() In circuit analysis, a short circuit is an ideal zero resistance, that will support any current with zero voltage across it.įor example, if I had a circuit with just a wire and a battery and it had a high voltage and low amperage, would this cause a short circuit in comparison to a circuit with low voltage and high amperage? For instance a PP3 or CR2032 battery, while it will be run down by a short circuit, is most unlikely to start a fire as a result. Given this, there may be some sense, hinted at in your question, that for high current batteries, a short circuit is an issue, where it is not for low current batteries. The wiring to a low current battery may not need protection, if the short-circuit current is low enough for any practical wire. The wiring to a high current battery, like a car battery for instance, will invariably be protected by a fuse, which opens in the event of a short circuit. At worst, the battery may catch fire, burst itself or its container, or the load start a fire. At best, the battery will be run down quickly. Any battery, whether a high voltage or low voltage battery, will be 'short-circuited' by putting a low or zero resistance load on it.Ī short circuit usually produces damaging conditions for the battery, and the load, if maintained for enough time. In the context of a battery (or any power source), we usually mean it to be a load that is far too large for the source. ![]() ![]() 'Short Circuit' gets used in two different ways.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |