Electromagnetic Induction

An inductance coil have the time constant $$4\sec$$ if it is cut into two equal parts and connected parallel then new time constant of the circuit:
What is a generator state the principle on which generators work 
A resistor R, an inductor L and a capacitor C are connected in series to an oscillator of frequency n. If the resonant frequency is $${n}_{r}$$,then the current lags behind voltage, when :
The magnetic induction in vacuum at a plane surface of a magnetic is equal to $$B$$ and the vector $$\vec{B}$$ forms an angle $$\theta$$ with the normal $$\vec{n}$$ of the surface (figure shown above). The permeability of the magnetic is equal to $$\mu$$.
A pair of parallel horizontal conducting rails of negligible resistance shorted at one end is fixed on a table. The distance between the rails is $$L$$. A conducting massless rod of resistance $$R$$ can slide on teh rails frictionlessly. The rod is tied to a massless string which passes over a pulley fixed to the edge of the table. A ass $$m$$ tied to the other end of the string hangs vertically. A constant magnetic field $$B$$ exists perpendicular to the table. If the system is released from rest. Calculate