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PhysicsJAMB UTME2001

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Earlier discussion

1 older comment kept for context.

Oluwaseun Adeyemi

for a parallel R and X, when R = 5Ω,

effective resistance R = 5X
5+X


and when R = 2Ω
effetive resistance R = 2X
2+X


Thus since E = I(R+r), and if r = 0 then E = IR

∴(i) E = 3(5X/(5+x)); (ii) E = 6(2X(2+x))

∴3(5X/(5+X)) = 6(2X/(2+X))

=> (5X/(5+X)) = 2(2x/(2+X))

∴ (5X/(5+X)) = (4X/(2+X))

5x(2+x) = 4x(5+x)

10x + 5x2 = 20x + 4x2

5x2 - 4x2 = 20x - 10x

=>x2 = 10x

∴x2 - 10x = 0

x(x - 10) = 0

∴ x = 0 or 10

∴ x = 10Ω