Question

when two resistors are joined in series the equivalent resistance is 40 ohm.when the same resistors are joined in parallel,the equivalent resistance is 7.5 ohm. Calculate the resistance of two resistors

Answer 1

The Answer is:

R₁: 10Ω & R₂: 30Ω

Let the 2 resistances be 'x' & 'y'.

Acc. to the formula of Combination of Resistances:

When 2 resistors are connected in series: Rnet = R₁ + R₂ + R₃ +..........+Rₙ

⇒ 40=x+y                                                   .........(i)

& when 2 resistors are connected in parallel:

1/Rnet = 1/R₁+ 1/R₂+ 1/R₃+..........+1/Rₙ

⇒ 7.5 = 1/(1/x + 1/y)

⇒15/2 =   (xy/x+y)                                      .........(ii)

On Solving (i) and (ii) we get....

x= 30Ω or 10Ω and y= 10Ω & 30Ω respectively....