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.
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.
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