lakha (ml29327) – HW#6 – Jaafari – (1444)
1
This
printout
should
have
10
questions.
Multiplechoice questions may continue on
the next column or page – find all choices
before answering.
001
10.0 points
How long does it take for 10 C of charge to
pass through a crosssectional area of a copper
wire if
I
= 2
.
8 A?
Correct answer: 3
.
57143 s.
Explanation:
Let :
I
= 2
.
8 A
and
Δ
Q
= 10 C
.
I
=
Δ
Q
Δ
t
Δ
t
=
Δ
Q
I
=
10 C
2
.
8 A
=
3
.
57143 s
.
002
10.0 points
A calculator is rated at 0.28 W when con
nected to 2.00 V battery.
What is the resistance of this device?
Correct answer: 14
.
2857 Ω.
Explanation:
Let :
P
= 0
.
28 W
and
Δ
V
= 2
.
00 V
.
P
=
(Δ
V
)
2
R
R
=
(Δ
V
)
2
P
=
(2 V)
2
0
.
28 W
=
14
.
2857 Ω
.
003
(part 1 of 2) 10.0 points
A string of 19 identical Christmas tree lights
are connected in series to a 120 V source. The
string dissipates 84 W.
What is the equivalent resistance of the
light string?
Correct answer: 171
.
429 Ω.
Explanation:
Let :
V
= 120 V
and
P
= 84 W
.
Resistance is
R
=
V
2
P
=
(120 V)
2
84 W
=
171
.
429 Ω
.
004
(part 2 of 2) 10.0 points
What is the resistance of a single light?
Correct answer: 9
.
02256 Ω.
Explanation:
Let :
n
= 19
.
R
=
n R
1
, so
R
1
=
R
n
=
171
.
429 Ω
19
=
9
.
02256 Ω
.
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 Fall '07
 ViolaRuck
 Charge, Ratio, Harshad number, Electrical resistance

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