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QPages 249-253: Q32: HC Verma: Concepts of Physics - Volume 2 Magnetic Field Due to a Current Pages 249-253: Q32 Solution: A circular loop of one turn carries a current of 5.00 A. If the …

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often confuse the magnetic field at the centre of a single circular loop with the field of a solenoid or a loop at a distance, using $B=mu_0 I/(2pi r)$ or $B=mu_0 I r^2/[2(r^2+z^2)^{3/2}]$ instead of the correct $B=mu_0 I/(2r)$. Always check that the formula you use corresponds to a single loop at its centre, and convert $0.200,$mT to $0.200 imes10^{-3},$T before substituting.

A circular loop of one turn carries a current of 5.00 A. If the magnetic field

B

at the centre is 0.200 mT, find the radius of the loop.

Step-by-Step Verified Solution

**Answer:**

r = 1.57

cm. **Step-by-Step Explanation:**

i = 5

A,

B = 0.2 \times 10^{-3}

T.

B = \frac{\mu_0 i}{2r} \Rightarrow r = \frac{\mu_0 i}{2B} = \frac{4\pi \times 10^{-7} \times 5}{2 \times 0.2 \times 10^{-3}} = 0.0157

m = 1.57 cm.

All Questions in this Chapter

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