Drag

# 物理代写｜PHYS 118 Electric fields

Q2.1 Three large, parallel planes of charge made from non-conducting material are
shown edge-on. The left plane has positive charge density (+𝜂), the middle plane
has negative charge density (−𝜂),, and the right plane has positive charge density
(+2𝜂),. The planes are so large that they can be considered infinite in extent.
Consider the direction to the right to be positive. Rank the electric fields from largest to smallest.

Note an electric field in the negative x-direction is smaller than an electric field in the
positive x-direction.

A. D>B>A>C
B. D>B>A=C
C. C>D>A=B
D. C>B=D>A
E. D>A=C>B
F. C>A=B=D

Explain:

Q2.2 Four point-charges are found on the corners of a square having sides of length
a, as shown in the Figure below. a) What is the direction of the electric field at point P?

The direction options are indicated by the legend to the right of the figure.

b) What is the magnitude of the electric field at point P?

Enter your formula in terms of 𝑘, 𝑄, and 𝑎.

Q2.3 A uniformly-charged insulating rod is bent into the shape of a semi-circle of
radius R, as depicted below. The total charge on the rod is +Q. There are no other
charges nearby. What can you say about the magnitude of the electric field at the center of the semi
circle?

A. 𝐸 = 𝑘𝑄/𝑅2
B. 𝐸 > 𝑘𝑄/𝑅2
C. 𝐸 < 𝑘𝑄/𝑅2
D. Not enough information to decide.

Explain:

Q2.4 The electric field lines that result from two charges are shown below a) Rank the magnitude of the electric fields, from strongest to weakest at the
positions shown (1, 2, 3).

A. 1>2>3
B. 1=2>3
C. 2>1>3
D. 3>2>1

Explain: