When source of sound and observer both are moving towards each other, the observer will hear

Water rises in a capillary tube of radius r upto ${ }^2$ height h . The mass of water in a capillary is m. The mass of water that will rise in capillary of radius $\frac{\mathrm{r}}{5}$ will be

Two similar wires of equal lengths are bent in the form of a square and a circular loop. They are suspended in a uniform magnetic field and same current is passed through them. Torque experienced by

A wire of length $L$ carries current $I$ along x - axis. A magnetic field $\overrightarrow{\mathrm{B}}=\mathrm{B}_0(\hat{\mathrm{i}}-\hat{\mathrm{j}}-\hat{\mathrm{k}}) \mathrm{T}$ acts on the wire. The magnitude of magnetic force acting on the wire is