Basic electricity question

[[Tycho?]]

I hope this isn't too stupid, but I have to learn somehow.

 

What would happen if you ran a house current back into the house?

 

When you plug in an appliance, current flows through the appliance (like a light bulb) and back into the outlet. What happens if you remove the appliance/resitor from that circuit (keeping the circuit itself intact)? Will current flow? Will it start a fire? Etc.

[Cap'n Refsmmat]

That would be the same thing as shorting it out. With no resistance, you'd suck up a lot of electricity very quickly. Most likely you'd blow a fuse or the circuit breaker.

 

This is what ground-fault interrupt outlets are for: if it's shorted out (which is what happens if you drop a hair dryer in the bathtub and electrocute yourself, or whatever), it cuts the current before you can get injured.

[ydoaPs]

i accidently did that once. my lamp fell of the shelf and went down the stairs. the wires got pulled out. the positive and negative touched, i saw a brilliant flash, then the power went out.

[[Tycho?]]

Yeah I thought it would blow a fuse. Ok thanks, questions answered.

[Douglas]

']

When you plug in an appliance' date=' current flows through the appliance (like a light bulb) and back into the outlet. What happens if you remove the appliance/resitor from that circuit (keeping the circuit itself intact)? Will current flow? Will it start a fire? Etc.[/quote']Current cannot flow unless there's a path from from the hot prong of the outlet to the ground prong of the outlet. The answer to both questions is NO.

[Cap'n Refsmmat]

He stated specifically "keeping the circuit itself intact."

[mmalluck]

And he also says "What happens if you remove the appliance/resitor from that circuit"

 

If you remove the load (open the circuit) the current can not continue to flow. Current depends on the voltage and load. The circuit can not 'be left intact' with the removal of the load.

 

Remember:

V=I/R

 

With wall sockets, the voltage is constant. As such, it's better to look at what the current is doing when we vary the load.

so....

I = V/R

 

So are you asking what would happen if you yanked the plug out of the wall while the lamp was on? or about jabbing forks into the electric socket?

 

The first one would result in nothing drastic. The removal of the load (our lamp) would see that the resistance across our circuit approaches infinity.

 

Going back to our equation:

 

I = V/R, we'll assume your on a 120v circuit, so yanking out the lamp would look something like...

 

I = (120 volts / Near Infinite Ohms), so no current will flow.

 

The second (jabbing a fork into the socket) would lead to a blown fuse or tripped circuit breaker. The fork looks like a load resistance of zero ohms (nearly).

 

I = (120 volts / nearly 0 Ohms), so tons of current flows.

 

Now in electrical circuits, current is directly related to the power the circuit consumes

 

Power = Current * Voltage

P= I*V

 

We have a high current, a fixed voltage, so that fork will be drawing lots of power and the fork will give off this power as heat. If the circuit breaker doesn't trip, nor the fuse blows, you'll end up with a smoldering fork or wall wiring.

[Thomas Kirby]

Let's get very technical here because I think that the distinction is very important. Ground Fault Circuit Interrupters are not made to deal with short circuits unless they also include a breaker, which some do. The ones that do are usually made for the breaker box and not for the outlet. The one thing that GFCI devices are for is to prevent potentially fatal electrical shocks. They detect current flowing to ground that is not supposed to flow to ground, presume that this current indicates a dangerous condition like a radio dropped in a bathtub, and shut down the current.

 

Some time just about now the National Electrical Code is going to include requirements for AFCI devices, Arc Fault Circuit Interrupters. They detect arcing, which can happen in a bad outlet, like one that someone has squirted paint into (don't ask me how I know, I just know). That arcing can cause very high temperatures and set fires. This can also happen in bad wiring in lamps and appliances. A chip that can detect the electronic signature of an electric arc, essentially broadband noise, can interrupt a circuit hopefully before a fire start. How it can distinguish between that and the noise generated by the brushes of an electric motor I don't know.

 

That would be the same thing as shorting it out. With no resistance' date=' you'd suck up a lot of electricity very quickly. Most likely you'd blow a fuse or the circuit breaker.

 

This is what ground-fault interrupt outlets are for: if it's shorted out (which is what happens if you drop a hair dryer in the bathtub and electrocute yourself, or whatever), it cuts the current before you can get injured.[/quote']

[[Tycho?]]

And yes, I'm reffering to the "fork in the socket" option here, thanks for the responses.