Download Exam B: Electric Charges, Forces and Fields Total points = 100

Exam B: Electric Charges, Forces and Fields
Total points = 100
PHY 162 General Physics II
Mercer University Physics – Fall 2014
Name: _________________________
Signature: _________________________
 SHOW ALL YOUR WORK: Answers without explanation will receive little or no credit.
 All numerical answers should be given as decimals. Please do not leave answers in terms of , fractions,
square roots, trig functions, or inverse trig functions.
 Except as noted, provide numerical answers that are either EXACT, or accurate to THREE
SIGNIFICANT FIGURES, or WITHIN 1% of the exact answer.
 Acceleration due to gravity at the Earth's surface:
 Fundamental unit of charge:
 Electrostatic constant:
 Permittivity of the vacuum:
 Electron mass:
A: (30 points) Coulomb’s Law
A particle with charge
, and
distances are
at the origin?
is at the origin. There are three other particles with charges
,
. Their positions
are
,
, and
, respectively. The
, and
. What is the total electric force acting on the particle
______________________
______________________
B: (20 points) Electric Force
Two large thin parallel plates have charge densities
, where
They are separated by a
distance
. What is the electric field between the plates, including direction? An electron enters
the region between the plates through a small opening in the left plate, with initial speed
.
What is the force on the electron, including direction? Does it reach the right plate?
IF YES, what is its speed as it hits the right plate? IF NO, how far does it travel before turning around?
 (6 points)
______________________, direction: Circle RIGHT or LEFT.
 (6 points)
______________________, direction: Circle RIGHT or LEFT.
 (8 points) Does it reach the right plate? Circle YES or NO.
IF YES:
IF NO:
______________________
______________________
C: (20 points) Three Parallel Plates
Three large thin parallel plates have charge densities
,
, and
, where
. Find the magnitude and direction of the electric field in each separate region: L (left),
ML (middle left), MR (middle right) and R (right).
 (5 points) (L)
______________________, direction: Circle LEFT or RIGHT
 (5 points) (ML)
______________________, direction: Circle LEFT or RIGHT
 (5 points) (MR)
______________________, direction: Circle LEFT or RIGHT
 (5 points) (R)
______________________, direction: Circle LEFT or RIGHT
D: (30 points) Spherically Symmetric Charge Distributions
D1. (14 points) Consider a uniformly-charged solid sphere with charge
Find the magnitude and direction of the electric field at
, and at
 (5 points) At
 (5 points) At
 (4 points) Plot of
,
,
and radius
. Plot the function
.
.
______________________, direction: Circle IN or OUT
______________________, direction: Circle IN or OUT
.
D2. (16 points) Consider a point charge (
) surrounded by a conducting shell. The shell has zero
net charge, inner radius
and outer radius
. Find the magnitude and
direction of the electric field at the indicated values. Plot the function
.
 (4 points) At
,
______________________, direction: Circle IN or OUT.
 (4 points) At
,
______________________, direction: Circle IN or OUT.
 (4 points) At
,
______________________, direction: Circle IN or OUT.
 (4 points) Plot of
.