Question

Two concentric current loops lie in the same plane. The smaller loop has a radius of 3 cm and a current of 12 A . The bigger loop has a current of 20 A . The magnetic field at the center of the loops is found to be zero, so the radius of the bigger loop is \( \qquad \) and if the radius of the bigger loop changed and became 8 cm and the two currents are in same directions, so the net magnetic field at the center of the two loops is \( \qquad \) \( \left(\mu=4 \pi \times 10^{-7} \mathrm{~Wb} /\right. \) A.m \( )(\pi=22 / 7) \) \begin{tabular}{|l|c|c|} \hline & The radius of the bigger loop & The net magnetic field \\ \hline (A) & 0.06 m & \( 4.08 \times 10^{-4} \mathrm{~T} \) \\ \hline (B) & 0.05 m & \( 4.08 \times 10^{-4} \mathrm{~T} \) \\ \hline (C) & 0.06 m & \( 1.06 \times 10^{-4} \mathrm{~T} \) \\ \hline (D) & 0.05 m & \( 1.06 \times 10^{-4} \mathrm{~T} \) \\ \hline \end{tabular}

          Two concentric current loops lie in the same plane. The smaller loop has a radius of 3 cm and a current of 12 A . The bigger loop has a current of 20 A . The magnetic field at the center of the loops is found to be zero, so the radius of the bigger loop is \( \qquad \) and if the radius of the bigger loop changed and became 8 cm and the two currents are in same directions, so the net magnetic field at the center of the two loops is \( \qquad \) \( \left(\mu=4 \pi \times 10^{-7} \mathrm{~Wb} /\right. \) A.m \( )(\pi=22 / 7) \)
\begin{tabular}{|l|c|c|}
\hline & The radius of the bigger loop & The net magnetic field \\
\hline (A) & 0.06 m & \( 4.08 \times 10^{-4} \mathrm{~T} \) \\
\hline (B) & 0.05 m & \( 4.08 \times 10^{-4} \mathrm{~T} \) \\
\hline (C) & 0.06 m & \( 1.06 \times 10^{-4} \mathrm{~T} \) \\
\hline (D) & 0.05 m & \( 1.06 \times 10^{-4} \mathrm{~T} \) \\
\hline
\end{tabular}

Two concentric current loops lie in the same plane. The smaller loop has a radius of 3 cm and a current of 12 A . The bigger loop has a current of 20 A . The magnetic field at the center of the loops is found to be zero, so the radius of the bigger loop is and if the radius of the bigger loop changed and became 8 cm and the two currents are in same directions, so the net magnetic field at the center of the two loops is (μ=4 π× 10^-7 Wb /. A.m )(π=22 / 7)

The radius of the bigger loop The net magnetic field

(A) 0.06 m 4.08 × 10^-4 T

(B) 0.05 m 4.08 × 10^-4 T

(C) 0.06 m 1.06 × 10^-4 T

(D) 0.05 m 1.06 × 10^-4 T

Added by Lisa B.

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