Create assignment, 00224, Homework 6, Feb 22 at 9:30 am
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The due time is Central
time.
Adding a Resistor
28:03, trigonometry, numeric,
>
1 min, nor
mal.
001
A loop circuit has a resistance of
R
1
and a cur
rent of 2 A. The current is reduced to 1
.
6 A
when an additional 3 Ω resistor is added in
series with
R
1
.
What is the value of
R
1
?
Correct answer: 12 Ω.
Explanation:
Let :
I
1
= 2 A
,
I
2
= 1
.
6 A
,
and
R
2
= 3 Ω
.
Let the current with
R
1
be
I
1
and the cur
rent with additional resistance
R
2
be
I
2
. Then
since the emf and the internal resistance of the
battery is a constant, we have
I
1
R
1
=
I
2
(
R
1
+
R
2
)
I
1
R
1
=
I
2
R
1
+
I
2
R
2
R
1
=
I
2
I
1

I
2
R
2
=
1
.
6 A
2 A

1
.
6 A
(3 Ω)
=
12 Ω
.
keywords:
Serway CP 18 06
28:04, trigonometry, numeric,
>
1 min, nor
mal.
002
Consider the circuit
I
30 V
S
18 Ω
9 Ω
6 Ω
12 Ω
Find the equivalent resistance.
Correct answer: 15 Ω.
Explanation:
I
E
S
R
2
R
3
R
4
R
1
Let :
R
1
= 12 Ω
,
R
2
= 18 Ω
,
R
3
= 9 Ω
,
and
R
4
= 6 Ω
.
R
2
,
R
3
and
R
4
are in parallel, so
1
R
234
=
1
R
2
+
1
R
3
+
1
R
4
=
R
3
R
4
+
R
2
R
4
+
R
2
R
3
R
2
R
3
R
4
R
234
=
R
2
R
3
R
4
R
3
R
4
+
R
2
R
4
+
R
2
R
3
Since
R
3
R
4
+
R
2
R
4
+
R
2
R
3
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 Spring '10
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 Physics, Work, SEPTA Regional Rail, Jaguar Racing, 1 min, ABCDA

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