Two point charges A and B of magnitude +8 $$\times$$ 10^$$-$$6 C and $$-$$8 $$\times$$ 10^$$-$$6 C respectively are placed at a distance d apart. The electric field at the middle point O between the charges is 6.4 $$\times$$ 10⁴ NC^$$-$$1. The distance 'd' between the point charges A and B is :

Resistance of the wire is measured as 2 $$\Omega$$ and 3 $$\Omega$$ at 10$$^\circ$$C and 30$$^\circ$$C respectively. Temperature co-efficient of resistance of the material of the wire is :

The space inside a straight current carrying solenoid is filled with a magnetic material having magnetic susceptibility equal to 1.2 $$\times$$ 10^$$-$$5. What is fractional increase in the magnetic field inside solenoid with respect to air as medium inside the solenoid?

Two parallel, long wires are kept 0.20 m apart in vacuum, each carrying current of x A in the same direction. If the force of attraction per meter of each wire is 2 $$\times$$ 10^$$-$$6 N, then the value of x is approximately :