Magnetic field at a distance $r$ from an infinitely long straight conductor carrying a steady current varies as

Consider a tightly wound $100$ turn coil of radius $10 \,cm$ carrying a current of $2 \,A$. The magnitude of the magnetic field at the centre of the coil is

$A$ semi-circular arc of radius $r$ and a straight wire along the diameter,both are carrying the same current $i$. Find out the magnetic force per unit length on the small element $P$,which is at the center of the diameter.

$A$ current of $4 \ A$ is passed through a square loop of side $5 \ cm$ made of a uniform manganin wire as shown in the figure. The magnetic field at the centre of the loop is

The magnetic field at the origin due to a current element $i \, d\vec{l}$ placed at position $\vec{r}$ is given by the Biot-Savart Law. Which of the following expressions correctly represent this magnetic field?
$(i) \, \left( \frac{\mu_0 i}{4\pi} \right) \left( \frac{d\vec{l} \times \vec{r}}{r^3} \right)$
$(ii) \, - \left( \frac{\mu_0 i}{4\pi} \right) \left( \frac{d\vec{l} \times \vec{r}}{r^3} \right)$
$(iii) \, \left( \frac{\mu_0 i}{4\pi} \right) \left( \frac{\vec{r} \times d\vec{l}}{r^3} \right)$
$(iv) \, - \left( \frac{\mu_0 i}{4\pi} \right) \left( \frac{\vec{r} \times d\vec{l}}{r^3} \right)$

$\frac{V \cdot s}{A \cdot m}$ is the unit of which physical quantity?