A current passes through a wire of non-uniform cross-section. Which of the following quantities are independent of the cross-section?
(a) The charge crossing in a given time interval
(b) Drift speed
(c) Current density
(d) Free-electron density
Answers
Given:
A current passes through a wire of non-uniform cross-section.
To find:
Which of the following quantities are independent of the cross-section?
Solution:
From given, we have,
(a) The charge crossing in a given time interval
The charge crossing in a given time interval is independent of the area of cross-section of the wire
(b) Drift speed
Drift speed is inversely proportional to the area of cross-section of the wire.
(c) Current density
Current density is inversely proportional to the area of cross-section of the wire.
(d) Free-electron density
The density of free electrons depends on the total number of free electrons per unit volume of the wire and is independent of the cross-section.
Thus options (a) The charge crossing in a given time interval and (d) Free-electron density are correct.