Q20 of 41 Page 461

Calculate the ratio of the equivalent resistance of the above two wires in parallel combination to that in series combination.

The resistance of the two wires are

R1 = 2Ω and R2 = 8Ω


When they are connected in series.



Equivalent resistance = R1 + R2


⇒ Req = 2 + 8 = 10 Ω.


Req in series = 10 Ω.


When they are connected in parallel.



Equivalent resistance=


⇒


⇒


⇒


Req in Parallel = 8/5 Ω.


Ratio of Parallel to series =


Hence the ratio of the Equivalent resistances in parallel to series is 4/25


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