Question

Two coils have combined resistance of 8ohm when connected in Series and 1.5ohm connected in parallel. find the resistance?​

Answer 1

To Find:

The value of individual resistance of coil

Solution:

Let the two resistance x and y.

In series,

x + y = 8

And in parallel, 1/1.5 = 1/x +1/y

Or 1.5 = x×y / x+y

Put y= 8- x.

1.5 = x×8-x / x +8-x

1.5 = 8x -x² / 8

Or 8×1.5 = 8x-x²

Or x²-8x+12 = 0

Solving Quadratic equation we get either

x= 6 Or x= 2.

If x=2 , y= 6.

Answer:

Hence the two resistances are 6 ohms and 2 ohms