The effective length of a magnet is $31.4 \mathrm{~cm}$ and its pole strength is $0.8 \mathrm{Am}$. The magnetic moment, if it is bent in the form of a semicircle is $\mathrm{Am}^{2}$A) $\quad 1.2$B)$1.6$C) $0.16$D) $0.12$

Home » The effective length of a magnet is and its pole strength is . The magnetic moment, if it is bent in the form of a semicircle is A) B)C) D)

The effective length of a magnet is $31.4 \mathrm{~cm}$ and its pole strength is $0.8 \mathrm{Am}$ . The magnetic moment, if it is bent in the form of a semicircle is $\mathrm{Am}^{2}$
A) $\quad 1.2$
B) $1.6$
C) $0.16$
D) $0.12$

Physics

The effective length of a magnet is $31.4 \mathrm{~cm}$ and its pole strength is $0.8 \mathrm{Am}$ . The magnetic moment, if it is bent in the form of a semicircle is $\mathrm{Am}^{2}$
A) $\quad 1.2$
B) $1.6$
C) $0.16$
D) $0.12$

Correct option is C $0.16$
The effective length of magnet $=31.4 \mathrm{~cm}$
Pole strength $\mathrm{m}=0.8 \mathrm{Am}$
Length of semi-circle $=\pi \frac{\mathrm{D}}{2}=1$
where, $\mathrm{D}=$ diameter of circle
$\begin{array}{l} \Rightarrow \mathrm{D}=\frac{21}{\mathrm{~m}} \\ =\frac{2 \times 314 \times 10^{-2}}{3.14} \\ \mathrm{D}=20 \times 10^{-2} \mathrm{~m} \end{array}$
Now, the magnetic moment
$\begin{array}{l} =\mathrm{ml}=\mathrm{mD} \\ =0.8 \times 20 \times 10^{-2} \\ =16.0 \times 10^{-2}=0.16 \mathrm{Am}^{2} \end{array}$

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