If R is the total resistance for a parallel circuit with two resistors of resistance r1 and r2, then one over R equals one over r subset one plus one over r subset two . Find the resistance, r1, if the total resistance R is 20 ohms, and r2 is 75 ohms. Round your answer to the nearest ohm if necessary.
(
1/R = 1/r1 + 1/r2
Plugging in the values for R (20 ohms) and r2 (75 ohms), we get:
1/20 = 1/r1 + 1/75
Now we can solve for r1:
1/r1 = 1/20 - 1/75
1/r1 = (75 - 20)/(20*75)
1/r1 = 55/1500
r1 = 1500/55
r1 ≈ 27.27
Therefore, the resistance r1 is approximately 27 ohms.