# How the current flow in a wire?

Saurabh Singh
askIITians Faculty 49 Points
10 years ago
A solid conductive metal contains a large population of mobile, or free, electrons. These electrons are bound to the metal lattice but not to any individual atom. Even with no external electric field applied, these electrons move about randomly due to thermal energy but, on average, there is zero net current within the metal. Given a plane through which the wire passes, the number of electrons moving from one side to the other in any period of time is on average equal to the number passing in the opposite direction.

When a metal wire is connected across the two terminals of a DC voltage source such as a battery, the source places an electric field across the conductor. The moment contact is made, the free electrons of the conductor are forced to drift toward the positive terminal under the influence of this field. The free electrons are therefore the current carrier in a typical solid conductor. For an electric current of 1 ampere, 1 coulomb of electric charge (which consists of about 6.242 × 1018 electrons) drifts every second through any plane through which the conductor passes.

The current I in amperes can be calculated with the following equation:

I = Q / t

where

Q is the electric charge in coulombs (ampere seconds)
t is the time in seconds

It follows that:

Q=It and t = Q/I

More generally, electric current can be represented as the time rate of change of charge, or

I = dQ/dt.

Thanks & Regards

Saurabh Singh,

B.Tech.

IIT Kanpur

Saurabh Singh
askIITians Faculty 49 Points
10 years ago
`A solid conductive metal contains a large population of mobile, or free, electrons. These electrons are bound to the metal lattice but not to any individual atom. Even with no external electric field applied, these electrons move about randomly due to thermal energy but, on average, there is zero net current within the metal. Given a plane through which the wire passes, the number of electrons moving from one side to the other in any period of time is on average equal to the number passing in the opposite direction.When a metal wire is connected across the two terminals of a DC voltage source such as a battery, the source places an electric field across the conductor. The moment contact is made, the free electrons of the conductor are forced to drift toward the positive terminal under the influence of this field. The free electrons are therefore the current carrier in a typical solid conductor. For an electric current of 1 ampere, 1 coulomb of electric charge (which consists of about 6.242 × 1018 electrons) drifts every second through any plane through which the conductor passes.The current I in amperes can be calculated with the following equation:I = Q / twhereQ is the electric charge in coulombs (ampere seconds)t is the time in secondsIt follows that:Q=It and t = Q/IMore generally, electric current can be represented as the time rate of change of charge, orI = dQ/dt.Thanks & RegardsSaurabh Singh,askIITians FacultyB.Tech.IIT Kanpur`
raju
59 Points
10 years ago
A wire functions as a conduit for electricity. In order for electricity to flow through a wire a difference in charge must exist. This difference in charge is measured in volts. Since Electricity is the flow of electrons, electricity will flow from negative charge to a positive charge.
raju
59 Points
10 years ago
Electrons are charged particles. They have a negative charge. An electron is normally part of an atom, so they can`t easily be moved around without taking the whole atom with them. But metals have a lot of electrons that aren`t tied to their atoms very tightly and they can roam around within a piece of metal. If we had a way to push them, they would flow as electric current. To understand where the push comes from, you need to know that positive and negative charges attract each other. If we could have a place where there are a bunch of extra electrons, that spot would have a significant negative charge. Also, if we have another spot that is missing a bunch of electrons, it would have a positive charge. An electron that isn`t tied tightly to an atom between these two places would be attracted to the side with the positive charge, and it would start to move. The area between the positive and negative spots would have what`s called an Electric Field caused by the charges there. This field is measured in volts (technically volts per meter). So voltage is the "pressure" that makes electrons move. Batteries and generators create the charge concentrations at their output terminals. (How they do that is a different story.) One terminal will be called "+" and the other "-", corresponding to positive and negative charges. If you connect the battery`s terminals to opposite ends of a piece or wire, that Electric Field follows the wire from positive to negative and all of the loose electrons in the wire start to move toward the positive end. Remember that the positive terminal of the battery is missing a bunch of electrons, so they flow into that terminal. The negative terminal of the battery has a bunch of extra electrons, so it replaces the ones that went out the other end of the wire into the battery. The battery (or generator) soaks up the electrons going from the wire into its positive terminal and keeps replacing the electrons that go into the other end of the wire from the negative terminal. The electrons moving through the wire are called the "electric current" which is measured in amperes, or "amps" for short. That`s about as simple as I can make the explanation. Voltage is the pressure, and current is the number of electrons per second that go through the wire. (It`s a really, really big number!) If you use water flowing through a hose as an analogy, the pressure (voltage) might be measured in pounds per square inch, and the current (amps) could be measured in gallons per minute.