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Problem
Problem
A constant voltage is applied to a series
R
R
R
-
L
L
L
circuit by closing the switch. The voltage across inductor (
L
=
2
L = 2
L
=
2
H) is 20 V at
t
=
0
t = 0
t
=
0
and drops to 5 V at 20 ms. The value of
R
R
R
in
Ω
\Omega
Ω
is (a)
100
ln
2
Ω
100 \ln 2 \Omega
100
ln
2Ω
(b)
100
(
1
−
ln
2
)
Ω
100 (1 - \ln 2) \Omega
100
(
1
−
ln
2
)
Ω
(c)
100
ln
4
Ω
100 \ln 4 \Omega
100
ln
4Ω
(d)
100
(
1
−
ln
4
)
Ω
100(1 - \ln 4) \Omega
100
(
1
−
ln
4
)
Ω
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