A 2 amp current is flowing through two different small circular copper coils having radii ratio $1: 2$. The ratio of their respective magnetic moments will be

A tightly wound 100 turns coil of radius $$10 \mathrm{~cm}$$ carries a current of $$7 \mathrm{~A}$$. The magnitude of the magnetic field at the centre of the coil is (Take permeability of free space as $$4 \pi \times 10^{-7} \mathrm{SI}$$ units):

A parallel plate capacitor is charged by connecting it to a battery through a resistor. If $$I$$ is the current in the circuit, then in the gap between the plates:

A long straight wire of length $$2 \mathrm{~m}$$ and mass $$250 \mathrm{~g}$$ is suspended horizontally in a uniform horizontal magnetic field of $$0.7 \mathrm{~T}$$. The amount of current flowing through the wire will be $$\left(\mathrm{g}=9.8 \mathrm{~ms}^{-2}\right)$$ :