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Phy 2061 Electricity & Magnetism, Fall 2008
Homework set #1.
Due at the start of class on Tuesday, August 26, 2008.
This is the first homework assignment of the semester and it is complete. It is also
due at the beginning of the first class meeting on Tuesday, August 26. I know that this is a
bit unusual, but I like to start the course at full speed talking about physics — I won’t be
talking much about the syllabus, because I assume that you will read it before the first class.
1. Carefully read the course syllabus — there is a link to it on the course home page.
On the homework to be handed in, state whether you carefully read it (2pts) or not
(1pt).
2. Carefully read the Math self-assessment—there is a link to it on the course home page.
On the homework to be handed in, state whether you carefully read it (2pts) or not
(1pt).
3. What is the magnitude of the force of gravity between an electron and a proton in a
hydrogen atom? Give your answer to within a factor of 10. Hint: The radius of a
hydrogen atom is known as the Bohr radius and is in a table in the inside front cover of
your text book. Hint: You really don’t need to use your calculator—I’m only asking
for an approximate answer.
4. With v = 1 × 10−16 c, evaluate
1−
q
1 − v 2 /c2 = ?
to two significant figures. Hint: The answer is not zero! Your calculator will probably
not be able to do this arithmetic.
5. Find the values of 0 and µ0 (these are known as the electric permittivity and the
magnetic permeability, respectively) on the inside, front cover of your textbook, and
√
evaluate 1/ µ0 0 to two significant figures. Be sure to show clearly and carefully how
the units simplify.
Hint: The unit “F” is a farad used to describe electric capacitance (more about this
in a week or so), and the unit “H” is a henry used to describe magnetic inductance
(more about this in a month or so). It is a fact that 1F × 1H = 1s2 , where “s” is a
second used to describe time intervals (you should be familiar with a “second” from
phy2060 :).
6. Assume that a is a constant, then evaluate the integral
Z L/2
−L/2
dz
= ? .
(z 2 + a2 )3/2