In a metre bridge experiment the balance point is obtained if the gaps are closed by $2$ $\Omega$ and $3\Omega$. A shunt of $X$ $\Omega$ is added to $3$ $\Omega$ resistor to shift the balancing point by $22.5$ cm. The value of $X$ is

A galvanometer has a current range of $10$ mA and a voltage range of $0.75$ V. To convert this galvanometer into an ammeter of range $10$ A, what is the shunt resistance?

Which of the following figure best represents the variation of magnetic susceptibility ($\chi$) with temperature for a diamagnetic substance?

A wire of length $L$ is bent in the form of a circular coil and current '$i$' is passed through it. This coil is kept in magnetic field. The torque acting on the coil will be maximum, when the number of turns is ___