song (shs546) – Homework 1 – weathers – (22202)
1
This
printout
should
have
8
questions.
Multiplechoice questions may continue on
the next column or page – find all choices
before answering.
001
10.0points
1) Two uncharged metal balls,
X
and
Y
, each
stand on a glass rod and are touching.
Y
X
2) A third ball carrying a positive charge, is
brought near the first two.
Y
X
+
3) While the positions of these balls are fixed,
ball
X
is connected to ground.
Y
X
+
4) Then the ground wire is disconnected.
Y
X
+
5) While
X
and
Y
remain in touch, the ball
carring the positive charge is removed.
Y
X
6) Then ball
X
and
Y
are separated.
Y
X
After these procedures, the signs of the
charge
q
X
on
X
and
q
Y
on
Y
are
1.
q
X
is positive and
q
Y
is neutral.
2.
q
X
is neutral and
q
Y
is neutral.
3.
q
X
is positive and
q
Y
is positive.
4.
q
X
is negative and
q
Y
is neutral.
5.
q
X
is neutral and
q
Y
is negative.
6.
q
X
is positive and
q
Y
is negative.
7.
q
X
is neutral and
q
Y
is positive.
8.
q
X
is negative and
q
Y
is negative.
cor
rect
9.
q
X
is negative and
q
Y
is positive.
Explanation:
When
the
ball
with
positive
charge
is
brought nearby, the free charges inside
X
and
Y
rearrange themselves.
The negative
charges are attracted and go to the right (
i.e.
move to
Y
), whereas the positive charges are
repelled and collect in the left hand side of the
system
XY
,
i.e.,
in
X
.
When we ground
X
, the positive charges
which have collected in
X
are allowed to es
cape (they strive to the left), whereas the
negative charges in
Y
are still held enthralled
by the positive charge on the third ball. We
break the ground.
Now we remove the third ball with positive
charge.
The charge on
Y
is redistributed in
the system
XY
,
i.e.
they share the negative
charge (equally if identical).
Finally we separate
X
and
Y
. The signs
of the charge on
X
and that on
Y
are both
negative.
002
10.0points
Four
point
charges,
each
of
magnitude
11
.
71
μ
C, are placed at the corners of a square
26 cm on a side.
If
three
of
the
charges
are
positive
and
one
is
negative,
find
the
magnitude
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
song (shs546) – Homework 1 – weathers – (22202)
2
of
the
force
experienced
by
the
negative
charge.
The value of Coulomb’s constant is
8
.
98755
×
10
9
N
·
m
2
/
C
2
.
Correct answer: 34
.
8979 N.
Explanation:
Let :
k
e
= 8
.
98755
×
10
9
N
·
m
2
/
C
2
,
d
= 26 cm = 0
.
26 m
,
and
Q
= 11
.
71
μ
C = 1
.
171
×
10
−
5
C
.
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '00
 Littler
 Charge, Work, Electric charge

Click to edit the document details