Create assignment, 99552, Homework 18, Apr 01 at 8:48 pm
1
This
printout
should
have
23
questions.
Multiplechoice questions may continue on
the next column or page – find all choices
before answering.
The due time is Central
time.
Charge in a Nickel
23:01, trigonometry, numeric,
>
1 min, nor
mal.
001
We want to find how much charge is on the
electrons in a nickel coin. Follow this method.
A nickel coin has a mass of about 5 g. Each
mole (6
.
02
×
10
23
atoms) has a mass of about
58 g.
Find the number of atoms in a nickel coin.
Correct answer: 5
.
18966
×
10
22
atoms.
Explanation:
Let :
N
a
= 6
.
02
×
10
23
atoms
,
M
= 58 g
,
and
m
= 5 g
.
Mass is
proportional
to the
number
of
atoms in a substance, so for
m
grams in
N
atoms in the nickel coin and
M
grams in
N
a
atoms in one mole, we have
m
M
=
N
N
a
N
=
m
M
N
a
=
(5 g)
(58 g)
(6
.
02
×
10
23
atoms)
=
5
.
18966
×
10
22
atoms
.
002
Find the number of electrons in the coin. Each
nickel atom has 28 electrons
/
atom.
Correct answer: 1
.
4531
×
10
24
electrons.
Explanation:
Let :
n
Ni
= 28 electrons
/
atom
.
If
n
Ni
electrons are in each Nickel atom,
then the total number of electrons
n
e
in the
coin is
n
e
=
N
n
Ni
=
(
5
.
18966
×
10
22
atoms
)
×
(28 electrons
/
atom)
=
1
.
4531
×
10
24
electrons
.
003
Find the magnitude of the charge of all these
electrons.
Correct answer: 232813 C.
Explanation:
Let :
q
e
=

1
.
60218
×
10

19
C
/
electron
.
The total charge
q
for the
n
e
electrons is
q
=
n
e
q
e
= (1
.
4531
×
10
24
electrons)
×
(

1
.
60218
×
10

19
C
/
electron
)
=

232813 C
,
which has a magnitude of
232813 C
.
keywords:
Charge in Lightning 03
23:01, trigonometry, numeric,
>
1 min, nor
mal.
004
A strong lightning bolt transfers about 25 C
to Earth.
The charge on an electron is 1
.
60218
×
10

19
C.
How many electrons are transferred?
Correct answer: 1
.
56038
×
10
20
.
Explanation:
Let :
q
= 25 C
.
The charge is proportional to the number
of electrons, so
q
=
n q
e
n
=
q
q
e
=

25 C

1
.
60218
×
10

19
C
=
1
.
56038
×
10
20
.
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Create assignment, 99552, Homework 18, Apr 01 at 8:48 pm
2
keywords:
AP EM 1998 MC 39 40
23:05,
trigonometry,
numeric,
>
1
min,
wordingvariable.
005
Two charged particles of equal magnitude
(+
Q
and

Q
) are fixed at opposite corners
of a square that lies in a plane (see figure be
low).
A test charge

q
is placed at a third
corner.
+
Q

q

Q
What is the direction of the force on the
test charge due to the two other charges?
1.
correct
2.
3.
4.
5.
6.
7.
8.
Explanation:
The force between charges of the same sign
is repulsive. The force between charges with
opposite signs is attractive.
+
Q

q

Q
The resultant force is the sum of the two
vectors in the figure above.
Therefore the
correct choice is
006
If
F
is the magnitude of the force on the test
charge due to only one of the other charges,
what is the magnitude of the net force act
ing on the test charge due to both of these
charges?
1.
F
net
= 0
2.
F
net
=
F
√
2
3.
F
net
=
F
4.
F
net
=
√
2
F
correct
5.
F
net
= 2
F
6.
F
net
= 3
F
7.
F
net
=
F
√
3
8.
F
net
=
3
F
2
9.
F
net
=
2
F
3
10.
F
net
=
2
F
√
3
Explanation:
The two individual forces form a right an
gle,
so the magnitude of the net force is
F
net
=
F
p
1
2
+ 1
2
=
√
2
F
.
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 Spring '08
 STAFF
 Physics, Charge, Force, Work, Correct Answer, Electric charge, Fnet

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