The magnetic effect of current was discovered by

$A$ coil of $n$ number of turns is wound tightly in the form of a spiral with inner and outer radii $a$ and $b$ respectively. When a current of strength $I$ is passed through the coil,the magnetic field at its centre is

What is the ratio of the electric field to the magnetic field produced by a moving point charge if its speed is $4.5 \times 10^{5} \; m/s$?

$A$ moving charge can produce which field? Explain.

Two long thin,parallel conductors carrying equal currents $I$ in the same direction are fixed parallel to the $x$-axis,one passing through $y = a$ and the other through $y = -a$. The resultant magnetic field due to the two conductors at any point is $B$. Which of the following are correct?

Two mutually perpendicular insulated conducting wires carrying equal currents $I$ intersect at the origin. The resultant magnetic induction at point $P(2 \ m, 3 \ m)$ will be: