NEET Physics Ampere's Law MCQ Question
Consider a long straight wire carrying a current I and an Amperian loop of radius r. If the loop is inside the wire (r < a), which of the following expressions correctly represents the magnetic field B at a distance r from the center of the wire?
B = μ0 I r / (2π a^2)
B = μ0 I / (2π r)
B = μ0 I r^2 / (2π a^2)
B = μ0 I a / (2π r^2)
Correct Answer
Detailed Explanation
Within the wire (r < a), the enclosed current I_e is less than the total current I and is given by I_e = I (r^2 / a^2). Using Ampere's Law, B (2π r) = μ0 I_e leads to B = μ0 I r / (2π a^2).
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