Two copper wires of different diameter are joined end to end. If a current flow in the wire combination, what happen to the drift velocity of the electrons when they move from the larger diameter to smaller diameter wire?
Answers
Answer:
Drift velocity of electrons in a solid times cross-section area is proportional to current.
What is the current in two conductors connected in series? The same.
What is the cross-section area of a thick wire compared with a thin wire? Smaller
So what happens to drift velocity at the junction of the wires? It increases.
Answer:
If the diameter of the wire decreases then the same density of moving charge (electrons) is in a volume whose length dimension has increased whilst it’s cross sectional area (CSA) has decreased; since volume of wire=CSA×length, a given charge must travel further in a given time, and velocity is distance over time so velocity is increased.
Compare this to a large diameter pipe connected to a small diameter pipe, the velocity of fluid in the pipe increases once area is constricted, easilly verified by taking a garden hose with water flowing through it, if you pinch the end the water squirts a longer distance.