Electromagnetic...

A thin copper wire of length 100 meters is wound as a solenoid of length $$\lambda$$ and radius r. Its self-inductance is found to be L. Now if the same length of wire is wound as a solenoid of length $$\lambda$$ but the radius r/2, then its self inductance will be:

Two coils of self inductance $$6 mH$$ and $$8 mH$$ are connected in series and are adjusted for highest coefficient of coupling. Equivalent self inductance $$L$$ for the assenbly is approximately 

A coil of inductance 300 mH and resistance $$2 \Omega$$  is connected to a source of voltage 2V. The current reaches half of its steady state value in

The inductance between $$A$$ and $$D$$ is:

The dimensions of self- induction are :

A conducting ring of radius r is rolling without slipping with a constant angular velocity $$ \omega $$ ( given figure). if the magnetic field strength is B and is directed into the page then the emf induced across PQ is:

A conducting wire frame is placed in a magnetic field which is directed in to the paper. The magnetic field increasing at a constant rate. The directions of induced current in wires AB and CD are:

The inductance of a solenoid $$0.5\ m$$ long of cross-sectional area $$20\ cm^2$$ and with $$500$$ turns is

The current in a coil decreases from  $$1 A$$  to  $$0.2 A .$$  In  $$10$$  sec. Calculate the coefficient of self-inductance. If induced emf is  $$0.4$$  volt.

If the magnetic flux linked up with a coil is changed by 40%, the energy storied in the coil changes by