Short Circuit
When a connection of very low to zero resistance is made between two points in a circuit, we have what is called a short circuit.
Since the current is voltage divided b resistance, V/0 = ∞. Since the current cannot really become infinite, the battery’s internal resistance r becomes the only resistance in the circuit.
Definition 2??
Two points (nodes) in a circuit are called a short circuit if the voltage between the 2 nodes is zero. An ideal voltage source with a zero voltage is equivalent to a short circuit.
New after learning from Ben Eater
Now that I have a better understanding of how Semiconductors work, I still beg the question: how do short circuits happen?
It’s when a large amount of current flows to somewhere it is not supposed to flow.
Like if you short circuit a battery?
what happens with a short circuit at atomic level? What causes the damage? It's just electrons moving super fast?
Firstly, electrons actually move super slowly. The drift velocity of individual electrons (the speed at which they actually move) is surprisingly slow, on the order of millimeters per hour in many cases. However, because of the sheer number of electrons involved, even a small drift velocity can result in a significant current.
Thus, the primary cause of damage in a short circuit is heat. When you have a sudden increase in current, it corresponds to a significant increase in power dissipation, mainly due to resistive heating (). Even if the resistance is very low, the squared term can cause the power, and therefore the heat, to be very large. This heat can cause materials to melt, burn, or even explode in extreme cases.
Other things:
- Molecular and Atomic Stress: The rapid generation of heat can cause rapid expansion in materials. This expansion can stress and break molecular bonds. For instance, in a wire experiencing a short circuit, the sudden heat can cause the metal to expand and even melt if the temperature gets high enough.
- Electromagnetic Effects: Large currents generate strong magnetic fields. In a short circuit scenario, these sudden and strong magnetic fields can induce voltages in nearby components or materials (due to Faraday’s law of electromagnetic induction). This can further contribute to the chaos and potential damage of a short circuit, especially in intricate electronic devices.
- Chemical Effects: In devices like batteries, a short circuit can lead to rapid chemical reactions. For instance, in a lithium-ion battery, a short circuit can cause the rapid release of stored chemical energy, leading t6. extreme heat and the potential for combustion or even explosion. The sudden heat and current can cause chemical structures to break down, leading to irreversible damage and, in extreme cases, the dangerous release of gases or other substances. Electromigration: Over time, the high current density in a short-circuited condition can actually cause atoms in a conductor to move, leading to a phenomenon known as electromigration. This could lead to the formation of voids or hillocks in the conductor, causing mechanical failure at the microscopic level.
- Breakdown of Semiconductor Junctions: In electronics that use semiconductor materials, a short circuit can cause currents that exceed the tolerances of the semiconductor junctions. This can lead to a breakdown of the controlled pathways that define the semiconductor’s behavior, leading to permanent damage.
In summary, while the atomic-level explanation of a short circuit boils down to an unusual, large flow of electrons (or ions in some cases), the consequences are much more than just “electrons moving super fast.” The heat generated due to the increased current can have a range of destructive effects at the atomic and molecular levels, leading to mechanical failure, chemical reactions, and other forms of degradation or damage.