Magnetic field intensity at the centre of coil of $50$ $turns$, radius $0.5\, m$ and carrying a current of $2\, A$ is

$PQRS$ is a square loop made of uniform conducting wire the current enters the loop at $P$ and leaves at $S$. Then the magnetic field will be

Biot-Savart, law indicates that the moving electrons (velocity $v$) produce a magnetic  field $B$ such that

A steady current $I$ goes through a wire loop $\mathrm{PQR}$ having shape of a right angle triangle with $\mathrm{PQ}=3 x, \mathrm{PR}=4 x$ and $\mathrm{QR}=5 x$. If the magnitude of the magnetic field at $\mathrm{P}$ due to this loop is $k\left(\frac{\mu_0 I}{48 \pi x}\right)$, find the value of $k$.

Circular loop of a wire and a long straight wire carry currents $I_c$ and $I_e$, respectively as shown in figure. Assuming that these are placed in the same plane, the magnetic fields will be zero at the centre of the loop when the separation $H$ is

A straight wire of diameter $0.5\, mm$ carrying a current of $1\, A$ is replaced by another wire of $1\, mm$ diameter carrying the same current. The strength of magnetic field far away is