The magnetic field of a given length of wire for a single turn coil at the centre is ' B ' then, its value for two turns coil for the same wire is:

Two point charges +2μC and -2μC are placed 10 cm apart. The electric field at the midpoint is:

A parallel plate capacitor made of circular plates is being charged such that the surface charge density on its plates is increasing at a constant rate with time. The magnetic field arising due to displacement current is :

Two identical charged conducting spheres $A$ and $B$ have their centres separated by a certain distance. Charge on each sphere is q and the force of repulsion between them is $F$. A third identical uncharged conducting sphere is brought in contact with sphere A first and then with B and finally removed from both. New force of repulsion between spheres $A$ and $B$ (Radii of $A$ and $B$ are negligible compared to the distance of separation so that for calculating force between them they can be considered as point charges) is best given as :

The electric potential at distance r from a point charge q is V = q/(4πε₀r). The electric field E is:

The current passing through the battery in the given circuit, is :