In which of the following devices, the eddy current effect is not used?

A long solenoid of diameter 0.1 m has 2 $$ \times $$ 10⁴ turns per meter. At the centre of the solenoid, a coil of 100 turns and radius 0.01 m is placed with its axis coinciding with the solenoid axis. The current in the solenoid reduces at a constant rate to 0 A from 4 A in 0.05 s. If the resistance of the coil is 10 $$\pi $$² $$\Omega $$, the total charge flowing through the coil during this time is

A uniform magnetic field is restricted within a region of rafius r. The magnetic field changes with time at a rate $${{d\overrightarrow B } \over {dt}}$$. Loop 1 of radius R > r encloses the region r and loop 2 of radius R is outside the region of magnetic field as shown in the figure. Then the e.m.f. generated is

A long solenoid has 1000 turns. When a current of 4 A flows through it, the magnetic flux linked with each turn of the solenoid is 4 $$ \times \,{10^{ - 3}}$$ Wb. The self-inductance of the solenoid is