In the ground state,an element has $13$ electrons in the $M$ shell. The element is

In a co-axial,straight cable,the central conductor and the outer conductor carry equal currents in opposite directions. The magnetic field is zero:

If $dx + dy = (x + y)(dx - dy)$,then $\log(x + y)$ is equal to

$A$ current $I$ flows in an infinitely long wire with a cross-section in the form of a semicircular ring of radius $R$. The magnitude of the magnetic induction along its axis is

If $f(x) = \sqrt{ax} + \frac{a^2}{\sqrt{ax}}$,then $f^{\prime}(a)$ is equal to

Which final cytochrome in the respiratory chain donates electrons to oxygen?