Though electrons are constantly in motion within metals, but there is no current until a potential difference is established across it. Explain why.
Electric Current in a Conductor:
When a potential difference is applied across the ends of the conductor, an electric current is established in the conductor, with a net flow of electrons through a cross section of the conductor.
Answer and Explanation:
In a metallic conductor, electric current is established only by applying the potential difference across it, which is explained as below:
- Although the free electrons in a conductor are in constant zig-zag motion, there is no net flow of electrons through a cross section in the absence of external potential difference.
- As soon as a potential difference is applied across the conductor, an electric field causes a net drift of free electrons in direction opposite to that of the electric field.
- As a result, a net flow of electrons is established through a cross section of the conductor, which constitutes an electric current.
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from CLEP Natural Sciences: Study Guide & Test PrepChapter 6 / Lesson 7