The radius of the current carrying circular coil is doubled keeping the current passing through it the same. Then the ratio of the magnetic field produced at the centre of the coil before the doubling of the radius to the magnetic field after doubling of the radius.
If the resultant of all external forces acting on a system of particles is zero, then from an inertial frame one can surely say that
The reverse current in the semiconductor diode changes from $$20 \mu \mathrm{A}$$ to $$40 \mu \mathrm{A}$$ when the reverse potential is changed from $$10 \mathrm{~V}$$ to $$15 \mathrm{~V}$$, then the reverse resistance of the junction diode will be :
A drone is flying due west, a little above the train, with a speed of $$10 \mathrm{~m} / \mathrm{s}$$. A 270 meter long train is moving due east at a speed of $$20 \mathrm{~m} / \mathrm{s}$$. The time taken by the drone to cross the train is