Problem Set is finalized!

Read Chapters 7 and 11.

1. a) Problem 7.5.**I**. First, correct the errors in
the equations. All v's should be the components perpendicular to the
shock front, and the vector in 7.10b should be a scalar.

b) In the
strong shock limit, determine the pressure P_{2}. Find the
upstream and downstream speeds in terms of the local sound speeds
c_{1} and c_{2} and comment.

2. Magnetic fields can always be derived from a vector potential
and can sometimes be derived from a scalar potential. In this problem,
you'll explore the conditions under which the latter is possible.

a) Let **A** = M_{B}sin(θ)r^{-2}
**&phi** where **&phi** is a unit vector in
the azimuthal direction, M_{B} is the magnetic moment, and
**B = ∇ x A** defines the magnetic vector potential
**A**. Find the magnetic field and compare to expressions
in the text for a magnetic dipole.

b) Show that **∇
⋅ B** = 0 for all possible **A**.

c)
Given **B = ∇**φ, evaluate **∇ x
B** and **∇ ⋅ B** and give condition
under which each is zero.

d) Compare your answers to c) to
Maxwell's equations and comment. Are your expressions valid deep
inside the planet?

3. a) Derive Eq. 7.16 from Maxwell's Equations.

b) Derive Equation 7.18 from Eq. 7.16. Determine the cgs units of the electrical conductivity σ_{o}.

4. Problem 11.4.**E**.

5. Problem 11.12.**I**.

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