We derived that the electric field due to an infinite sheet with charge density σ was as follows:
E(z)={σ2ε0ˆkif z > 0−σ2ε0ˆkif z < 0
What does that tell you about the difference in the field when we cross the sheet, E(+z)−E(−z)?
it's zero
it's σε0
it's -σε0
it's +σε0ˆk
it's -σε0ˆk
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Homework 2 solutions posted
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For me, the second homework was ...
fairly straight-forward; lower difficulty than I expected.
challenging, but at the level of difficulty I expected
a bit more difficult than I expected, but still manageable
much more difficult than I expected.
I spent ... hours on the second homework.
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Electric Potential
Which of the following two fields has zero curl?
I
II
Both do.
Only I is zero
Only II is zero
Neither is zero
???
What is the curl of the vector field, v=cˆϕ, in the region shown below?
non-zero everywhere
zero at some points, non-zero at others
zero curl everywhere
What is the curl of this vector field, in the red region shown below?
non-zero everywhere in the box
non-zero at a limited set of points
zero curl everywhere shown
we need a formula to decide
What is the curl of this vector field, v=csˆϕ, in the red region shown below?
non-zero everywhere in the box
non-zero at a limited set of points
zero curl everywhere shown
Is it mathematically ok to do this?
E=14πε0∫Vρ(r′)dτ′(−∇1R)
⟶E=−∇(14πε0∫Vρ(r′)dτ′1R)
Yes
No
???
If ∇×E=0, then ∮CE⋅dl=
0
something finite
∞
Can't tell without knowing C
Can superposition be applied to electric potential, V?
Vtot?=∑iVi=V1+V2+V3+…
Yes
No
Sometimes
We derived that the electric field due to an infinite sheet with charge density σ was as follows:
E(z)={σ2ε0ˆkif z > 0−σ2ε0ˆkif z < 0
What does that tell you about the difference in the field when we cross the sheet, E(+z)−E(−z)?
it's zero
it's σε0
it's -σε0
it's +σε0ˆk
it's -σε0ˆk
CORRECT ANSWER: D
Makes for a good discussion about cross one direction versus the other