Phys102
Term: 122
Online HW-Ch023-Lec01
Q1:
A point particle with charge q is placed inside a cube but not at its center. The
electric flux through any one side of the cube:
A. is zero
B. is q/ε 0
C is q/4ε 0
+q
D. is q/6ε 0
E. cannot be computed using Gauss' law
Ans:
𝐄
Q2:
A physics instructor in an anteroom charges an electrostatic generator to 25 µC, then
carries it into the lecture hall. The net electric flux in N m2/C through the lecture hall
walls is: (take the value of ε 0 as 8.85 x 10-12 in SI unit)
Ans:
q
25 × 10−6
Ø= =
= 2.8 × 106
−12
ε0 8.85 × 10
Q3:
A round wastepaper basket with a 15-cm radius opening is in a uniform electric field
of 300N/C, perpendicular to the opening. The magnitude of total flux through the
sides and bottom, in SI unit, is:
E
Ans:
Since the electric field is perpendicular to the opening the angle between the electric
field and any area vector in the round surface will be 90° and hence there will be no
flux through the sides.
Therefore the flux through the bottom is:
∅ = �E⃗. �A⃗ = EAcos(0) = EA = 500 × π0.152 = 21
KFUPM-Physics Department
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