Which scientist established that electricity and magnetism are interrelated?

The intensity of the magnetic induction field at the centre of a single turn circular coil of radius $5 \,cm$ carrying a current of $0.9 \,A$ is:

An electron makes a full rotation in a circle of radius $0.8 \ m$ in one second. The magnetic field at the centre of the circle is $(\mu_0 = 4 \pi \times 10^{-7} \text{ SI units})$.

Two straight infinitely long current-carrying wires are kept along the $z-$axis at the coordinates $(0, a, 0)$ and $(0, -a, 0)$ respectively, as shown in the figure. The current in each wire is equal and directed along the negative $z-$axis (into the plane of the paper). The variation of the magnetic field on the $x-$axis will be approximately:

What is the magnetic field at a distance $R$ from a coil of radius $r$ carrying current $I$ along its axis?

The dimension of the magnetic field intensity $B$ is