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Question : 22
Total: 36
For the series combination of three resistors establish the relation :
R = R 1 + R 2 + R 3
where the symbols have their usual meanings.
Calculate the equivalent resistance of the combination of three resistors of6 Ω , 9 Ω 18 Ω
where the symbols have their usual meanings.
Calculate the equivalent resistance of the combination of three resistors of
Solution:
Same current (I) flows through different resistances, when these are joined in series, as shown in the figure.R
V = IR
Also,V 1 = I R 1 , V 2 = I R 2 , V 3 = I R 3
∵ V = V 1 + V 2 + V 3
∴ IR = IR 1 + IR 2 + IR 3
⇒ IR = I ( R 1 + R 2 + R 3 )
∴ R = R 1 + R 2 + R 3
Now,R 1 = 6 Ω , R 2 = 9 Ω , R 3 = 18 Ω
In parallel combination,
=
+
+
⇒
=
+
+
=
=
=
⇒
=
⇒ R = 3 Ω
Let
Also,
Now,
In parallel combination,
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