Which is the wrong unit of magnetic dipole moment?

Options

A. ampere `"metre"^(2) (Am^(2))`
B. newton metre/tesla
C. newton `"metre"^(3)`/weber
D. joule tesla

Answer

D

Explanation

(1) M is generally expressed in `Am^(2)`
(2) `("N-m")/("tesla")=("joule")/("tesla")`
(3) `(Nm^(3))/(Wb)=(Nm)/("Wb/m"^(2))=(Nm)/("tesla")`
and `:'` torque acting on a magnet
`tau=MB sin theta` for `theta=90^(@)`, we get the maximum torque.
`:.` Max `tau=MB" ":. M=tau/B=("N-m")/("tesla")`
Thus `Nm^(3)`/Wb is also a unit of M and hence joule-tesla is a wrong unit.