Concept explainers
Figure P26.6 represents a section of a conductor of nonuniform diameter carrying a current of I = 5.00 A. The radius of cross-section A1 is r1 = 0.400 cm. (a) What is the magnitude of the current density across A1? The radius r2 at A2 is larger than the radius r1 at A1. (b) Is the current at A2 larger, smaller, or the same? (c) Is the current density at A2 larger, smaller, or the same? Assume A2 = 4A1. Specify the (d) radius, (e) current, and (f) current density at A2.
Figure P26.6
(a)
The magnitude of the current density across
Answer to Problem 6P
The magnitude of the current density across
Explanation of Solution
Given information: Current carried by a conductor is
Write the expression for the area of cross section of a conductor.
Here,
Substitute
Thus, the area of cross section of a conductor is
Formula to calculate the current density across
Here,
Substitute
Thus, the magnitude of the current density across
Conclusion:
Therefore, the magnitude of the current density across
(b)
The reason that the current at
Answer to Problem 6P
The current at
Explanation of Solution
Given information: Current carried by a conductor is
The current is not depending on cross sectional area. So, the current at
Thus, the density at
Conclusion:
Therefore, the density at
area. So, the current at
(c)
The reason that the current density at
Answer to Problem 6P
The current density at
Explanation of Solution
Given information: Current carried by a conductor is
From equation (2),
Formula to calculate the current density across
Here,
Formula to calculate the current density across
Here,
From above relations, the current density is inversely proportional to area of cross section. From the figure given in the question, it is shown that:
Hence, the current density at
Thus, the current density at
Conclusion:
Therefore, the current density at
(d)
The radius of cross section at
Answer to Problem 6P
The radius of cross section at
Explanation of Solution
Given information: Current carried by a conductor is
It is given that the expression for the crossectional area is:
From equation (1),
Write the expression for the area of cross section of a conductor
Write the expression for the area of cross section of a conductor
Here,
Substitute
Substitute
Thus, the area of cross section of a conductor is
Thus, the radius of cross section at
Conclusion:
Therefore, the radius of cross section at
(e)
The current for cross section at
Answer to Problem 6P
The current for cross section at
Explanation of Solution
Given information: Current carried by a conductor is
The current is not depending on cross sectional area. So, the current at
Thus, the current for cross section at
Conclusion:
Therefore, the current for cross section at
(f)
The magnitude of the current density across
Answer to Problem 6P
The magnitude of the current density across
Explanation of Solution
Given information: Current carried by a conductor is
Write the expression for the area of cross section of a conductor
Here,
Substitute
Thus, the area of cross section of a conductor is
Formula to calculate the current density across
Substitute
Thus, the magnitude of the current density across
Conclusion:
Therefore, the magnitude of the current density across
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