In the london equation, it is postulated that the current density inside a superconductor is proportional to the vector potential, i. e., j =-aa. (a) from the london equation and the maxwell equations, derive the meissner effect. in other words, prove that the magnetic field inside a bulk superconductor is 0 when there is an applied static magnetic outside. [10] (b) now consider a superconducting plate. an external magnetic field b is applied parallel to the plate. derive the expression for b(x) inside the superconducting plate, if the plate is placed perpendicular to the x-axis.

You are still fascinated by the process of inkjet printing, as described in the opening storyline for this chapter. you convince your father to take you to his manufacturing facility to see the machines that print expiration dates on eggs. you strike up a conversation with the technician operating the machine. he tells you that the ink drops are created using a piezoelectric crystal, acoustic waves, and the plateau-rayleigh instability, which creates uniform drops of mass m = 1.25 ✕ 10−8 g. while you don't understand the fancy words, you do recognize mass! the technician also tells you that the drops are charged to a controllable value of q and then projected vertically downward between parallel deflecting plates at a constant terminal speed of 20.0 m/s. the plates are ℓ = 2.15 cm long and have a uniform electric field of magnitude e = 6.40 ✕ 104 n/c between them. noting your interest in the process, the technician asks you, "if the position on the egg at which the drop is to be deposited requires that its deflection at the bottom end of the plates be 0.17 mm, what is the required charge on the drop (in c)? " you quickly get to work to find the answer. (neglect the force of gravity.)