Question 1174000: The current (I) in an electric circuit is inversely proportional to the resistance (R). If the resistance is 8 ohms when the current is 0.25 ampere, find the resistance when the current is 1.2 amperes. (Round your answer to two decimal places.)
Answer by Theo(13342)   (Show Source):
You can put this solution on YOUR website! formula for inverse proportion is y = k / x.
let y = r and let x = i.
formula becomes r = k / i.
r = 8 when i = .25 and the formula becomes:
8 = k / .25
solve for k to get:
k = .25 * 8 = 2
k is the constant of variation.
when i = 1.2, the formula becomes.
r = 2 / 1.2
solve for r to get:
r = 1.66667.
you can also use the formula of i1/i2 = r1/r2 for direct variation and i1/i2 = r2/r1 for inverse variation.
let (i1,r1) = (.25,8)
let i2,r2) = (1.2,x)
with direct variation, i1/i2 = r1/r2 becomes .25/1.2 = 8/x
solve for x to get x = 8 * 1.2 / .25 = 38.4
with inverse variation, i1/i2 = r2/r1 becomes .25/1.2 = x/8
solve for x to get x = 8 * .25 / 1.2 = 1.66667, same as you got using the inbverse variation formula of r = i / i.
here's a reference on direct and inverse variation.
https://www.purplemath.com/modules/variatn.htm
let me know if you have any further questions regarding this.
theo
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