A long straight wire carrying a current of $$25 \mathrm{~A}$$ rests on the table. Another wire PQ of length $$1 \mathrm{~m}$$ and mass $$2.5 \mathrm{~g}$$ carries the same current but in the opposite direction. The wire PQ is free to slide up and down. To what height will wire PQ rise? ($$\mu_0=4 \pi \times 10^{-7}$$ SI unit)

Two parallel conducting wires of equal length are placed distance 'd' apart, carry currents '$$\mathrm{I}_1$$' and '$$\mathrm{I}_2$$' respectively in opposite directions. The resultant magnetic field at the midpoint of the distance between both the wires is

An electron and a proton having the same momenta enter perpendicularly into a magnetic field. What are their trajectories in the field?

A solenoid 2 m long and 4 cm in diameter has 4 layers of windings of 1000 turns each and carries a current of 5 A. What is the magnetic field at its centre along the axis? [$$\mu_0=4\pi\times10^{-7}$$ Wb/Am]