Magnetic shielding is done by surrounding the instrument to be protected from magnetic field by

In the given figure, the equivalent capacitance between points A and B is

If work done in blowing a soap bubble of volume $$V$$ is $$W$$, then the work done in blowing the bubble of volume $$2 \mathrm{~V}$$ from same soap solution is

Which one of the following is based on convection?