Hello guys how are you all doing.
I have a question of the type when you deeply think and try to understand such minor things to have a clearer picture. My question is that, I know that a load, such as a boiler, draws an appropriate current from a voltage source according to Ohm's law. If that's the way, then why we face short circuits. What exactly happen??
For example if we have a 10 kV source and connected a 2 ohm load, what would happen?

Finally, I frequently have this type of questions but I'm not sure that this is the appropriate section to ask? if it wasn't, sorry in advance and please direct me to the right section.

 

Given the nature of the question and why you are asking it (to learn), this is a reasonable place to post it. The General Electronics Chat would also have been okay.

If you connect a 10 kV source to a 2 Ω load, then if nothing goes wrong you will get a current of 5000 A through both. If the source can't supply 5000 A, then something will happen. The voltage may drop to a point that corresponds to the current that it CAN supply, or circuitry might shut the supply down completely, or a breaker/fuse might open, or the supply might be damaged or destroyed, perhaps catastrophically. You also have the potential for things happening on the other end. If the load isn't capable of tolerating 10 kV across it, it might flash over with an electric arc. If it can't handle 5000 A flowing though it (and the resulting 50 MW of power being dissipated in it) then it might fail, probably in a spectacular fashion that leaves you with a smoking mess where the load used to be.

 

Shorts happen because current follows ohms law....AND because current is lazy. It will take an easier path if it can find one. You must keep current corralled.

 

Hello guys how are you all doing.
I have a question of the type when you deeply think and try to understand such minor things to have a clearer picture. My question is that, I know that a load, such as a boiler, draws an appropriate current from a voltage source according to Ohm's law. If that's the way, then why we face short circuits. What exactly happen??
For example if we have a 10 kV source and connected a 2 ohm load, what would happen?

Finally, I frequently have this type of questions but I'm not sure that this is the appropriate section to ask? if it wasn't, sorry in advance and please direct me to the right section.

What will likely happen if the 10kV source can supply the current to a 2 ohm load without shutting down in an instant?

It's very likely in a short circuit that energy from the source supply will flow and be dissipated in a (small) part of the circuit not designed to handle high power levels for long periods of time.

Ohm's law is the electrical equivalent to mechanical laws and mechanical behavior. A large truck with a large engine has the potential to move a large load in the bed of the truck. If the load is one person then the required extra power from the engine is small to accelerate from 0-60 mph. If the truck if fully loaded with 2000 kg of rocks the extra engine power needed with be much higher. If you vastly overload the truck the engine might fail like in a short circuit.

 

Hello guys how are you all doing.
I have a question of the type when you deeply think and try to understand such minor things to have a clearer picture. My question is that, I know that a load, such as a boiler, draws an appropriate current from a voltage source according to Ohm's law. If that's the way, then why we face short circuits. What exactly happen??
For example if we have a 10 kV source and connected a 2 ohm load, what would happen?

Finally, I frequently have this type of questions but I'm not sure that this is the appropriate section to ask? if it wasn't, sorry in advance and please direct me to the right section.

Hi,

Shorts are a funny part of electronics. The definition often depends on the application or theory being addressed at the time.
In your example with the 10kv source, a 2 ohm load may very well look like a short circuit to the source and so it may shut down to protect itself. If that was a CRT television for example, the circuit may shut down to avoid bigger problems. If that was a power line however, it may be an acceptable load.
One of my power supplies (actually two but they are the same model) will shut down with a 1 ohm load even though it is not a true short of zero Ohms.

 

For example if we have a 10 kV source and connected a 2 ohm load, what would happen?

It also depends on the nature of the device contain the load.
There are some devices that use what could be called a short circuit in order to operate!.
Max.

 

Hi,

Shorts are a funny part of electronics.

There are times when they seem to be alive.

Exactly how shorts or large transients behave in large high power systems is very complex. I think the initial event for this was a lightning strike on a transmission tower.

 

It also depends on the nature of the device contain the load.
There are some devices that use what could be called a short circuit in order to operate!.
Max.

Could you please elaborate Max?

 

Could you please elaborate Max?

For one, I always think of an induction motor at the point of switch on representing a transformer with a shorted turn secondary, not only do you have the winding inrush current but you have the reflected load of a shorted turn (rotor) secondary which does not start to decrease until the rotor starts revolving.
If you were to replace the rotor with just solid iron it would be a relatively low current choke with nothing moving.
It requires the very high rotor current to get it rotating.
Max.

 

Every incandescent light bulb is a pretty good short until it heats up some and begins to incandes.

 

Every incandescent light bulb is a pretty good short until it heats up some and begins to incandes.

I don't think I'd go that far. The cold resistance of a 60 W (120 VAC) incandescent is typically in the 70 Ω range.

 

Hi again,

nsaspook:
We used to have a saying in school, shorts look better on girls than in circuits
Ok we didnt really say that, but we were always thinking it

WBahn:
Yeah i have to agree. I measured around 10 ohms on a 100 watt 120v bulb which would draw a very brief 12 amps but i still would not call that a short unless i was being very sarcastic.

 

@nsaspook Your correct about that 2011 night in fort worth.

Here is another picture from that night ....

Source: CBSNews 11 DFW

 

@nsaspook Your correct about that 2011 night in fort worth.

Here is another picture from that night ....

Source: CBSNews 11 DFW

Only 5.000 people in black out after so many going out of service? It sounds unreal.

 

Only 5.000 people in black out after so many going out of service? It sounds unreal.

Obviously a cover story for the truth.

Spoiler

 

There are times when they seem to be alive.

Exactly how shorts or large transients behave in large high power systems is very complex. I think the initial event for this was a lightning strike on a transmission tower.

War of the Worlds?

 

Obviously a cover story for the truth.

Spoiler

Propellers???!