Question

Why doesn't current flow in an open circuit? Let's say I have a metal wire AB. The ends A n B are at the same potential(possibly 0v or something else) and hence no current flows. Now if i attach the positive terminal of a battery to end A, then A is at say V volts and B is at some other volt. Clearly there is a potential difference. Metals have a number of free electrons. Why dont they go the positive terminal and neutralise the charges? Why is it necessary to have a closed loop for current to flow??

Answer 1

Nice question! let's think together (I don't know either) but it makes me remember of a capacitor. When you charge a capacitor there is a transition state while the charges DO flow and a current appears. Maybe here is the same thing!

Answer 2

Sure Nachofq, lets work it out. My roomies gave the reason as to why the current doesn't flow is because the end B also attains the potential V volts. But I cannot understand this. How come the potential gets translated to the end of the wire B while not affecting the metal wire at all. but as soon I connect a ground, the electrons rush to the positive terminal producing a spark n burning the wire. What is happening?

Answer 3

As for your question of capacitor, the current through a capacitor is explained by Maxwell using a concept called displacement current. He states that , for a given capacitor at a high frequency, current starts to flow in the circuit. If we measure the voltage across the cap, then we find that it follows the input but with a lag. He said that a displacement current flows inside the capacitor and completes the circuit. In reality , a current does not flow.
I am reading Maxwells eqn. If i find out an answer, ll let u know..

Answer 4

you have to realize something that although the potential is equal there is no conducting medium between the two wires
another thing actually if you brought a battery and connected it with an open circuit current will not flow and potential difference between the two wires is not zero at all it equals to the battery voltage
a potential difference of more than 30 KV/CM is needed to break down air and to make current flow once this potential difference (gradient) is reached then a current will flow in the air and the potential difference between the two wires will be zero

Answer 5

So in this open circuit, why isn't there a current? A few things are wrong.

I believe the current does flow to an extent, but stops very shortly before it can suck out enough electrons to cause the wire to become positively charged. The reason is because within the battery the opposite sides are balanced by an electrolyte solution that's governed by redox reactions. Basically there's a salt bridge between the cathode and anode that allows electrons to be donated and accepted on either side of the battery's terminals. In order to be thermodynamically stable you have to give and receive electrons at the same time, so if you're only accepting or gaining electrons, you shift the redox reaction's equilibrium to create more anions or cations depending on which end is attached and lose the reaction's gradient as it starts to accumulate more and more of one type without the other type being taken away.

I hope that explains it well enough, I'll try to reread a little bit and see if I can understand it better myself, because I'm kind of unsure.