Q11. A long straight wire of circular cross section with radius 'a' carries steady current 'I' which

Q: What is the correct answer for CUET UG Physics Q11?

The correct answer is d. For a long straight wire of circular cross-section with radius 'a' carrying a uniformly distributed steady current 'I':1. **Inside the wire (r a):** The magnetic field (B) decreases inversely with the distance 'r' from the axis

Q: Q11. A long straight wire of circular cross section with radius 'a' carries steady current 'I' which is uniformly distributed across the cross-section. The magnetic field in the region r …

The correct answer is d. For a long straight wire of circular cross-section with radius 'a' carrying a uniformly distributed steady current 'I':1. **Inside the wire (r a):** The magnetic field (B) decreases inversely with the distance 'r' from the axis

Q: What are the options for this CUET UG Physics question?

A. [Graph showing B as constant and then decreasing as r increases] · B. [Graph showing B as increasing and then decreasing sharply as r increases] · C. [Graph showing B as increasing and then decreasing gradually as r increases] · D. [Graph showing B as increasing linearly from 0 for r a]

Question

Q11. A long straight wire of circular cross section with radius 'a' carries steady current 'I' which is uniformly distributed across the cross-section. The magnetic field in the region r < a and r > a is represented by:
(a) B vs r graph where B is constant then decreases
(b) B vs r graph where B increases then decreases sharply
(c) B vs r graph where B increases then decreases gradually
(d) B vs r graph where B increases linearly then decreases as 1/r

FirstInTest · Accepted Answer

For a long straight wire of circular cross-section with radius 'a' carrying a uniformly distributed steady current 'I':1.  **Inside the wire (r < a):** The magnetic field (B) increases linearly with the distance 'r' from the axis of the wire. The formula is B = (μ₀Ir) / (2πa²), so B ∝ r.2.  **Outside the wire (r > a):** The magnetic field (B) decreases inversely with the distance 'r' from the axis of the wire. The formula is B = (μ₀I) / (2πr), so B ∝ 1/r.Combining these, the magnetic field starts at zero at the center (r=0), increases linearly to a maximum value at the surface (r=a), and then decreases hyperbolically (as 1/r) outside the wire. Option (d) best represents this behavior visually, showing a linear increase from r=0 to r=a, and then a 1/r decrease for r>a.

Answer

[Graph showing B as constant and then decreasing as r increases]

Answer

[Graph showing B as increasing and then decreasing sharply as r increases]

Answer

[Graph showing B as increasing and then decreasing gradually as r increases]

Answer

[Graph showing B as increasing linearly from 0 for r<a, and then decreasing as 1/r for r>a]

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