You have three resistors of values 2 Ω, 3 Ω and 5 Ω. How will you join them so that the total resistance is more than 7 Ω?
Calculate the equivalent resistance.
Topic: Current, resistance and circuits
Answer
Given: resistors of 2 Ω, 3 Ω and 5 Ω, joined so that the total is more than 7 Ω.
The largest possible total comes from joining all three in SERIES.
For resistors in series: R = R₁ + R₂ + R₃ = 2 + 3 + 5 = 10 Ω
Equivalent resistance = 10 Ω
Series adds, parallel reduces. A series combination is always LARGER than the biggest single resistor, and a parallel combination is always SMALLER than the smallest one. That single fact answers the question before you calculate anything: only series can beat 7 Ω.
Use it as a check on every circuit answer. If you work out a parallel combination of 3 Ω and 6 Ω and get 9 Ω, you have added when you should have used the product-over-sum rule — the answer has to be under 3 Ω.