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You are given several identical resistances each of value R = 10 W and each capable of carrying a maximum current of one ampere. It is required to make a suitable combination of these resistances of 5 W which can carry a current of 4 ampere. The minimum number of resistances of the type R that will be required for this job is (a) 4 (b) 10 (c) 8 (d) 20



You are given several identical resistances each of value R = 10W and each capable of carrying a maximum current of one ampere. It is required to make a suitable combination of these resistances of 5W which can carry a current of 4 ampere. The minimum number of resistances of the type R that will be required for this job is


        (a)    4     


(b)    10


(c)    8     


(d)    20


Grade:upto college level

1 Answers

Aditi Chauhan
askIITians Faculty 396 Points
10 years ago

(c)

To carry a current of 4 amperes, we need four paths, each carrying a current of one ampere. Let r be the resistance of each path. These are connected in parallel. Hence, their equivalent resistance will be r/4. According to the given problem

 r/4=5

r=20

For this propose two resistances should be connected. There are four such combinations. Hence, the total number of resistance = 4 x 2 =8

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