Practice portal › Current Electricity › Combination of Resistors

You are given 10 resistors each of resistance 2 Ω. First they are connected to obtain the minimum possible resistance. Then they are connected to obtain the maximum possible resistance. The ratio of the maximum and minimum resistance is ____.

Asked in GUJCET 2018 · Series and parallel combinations

• (1) 100
• (2) 10
• (3) 2.5
• (4) 25

Step-by-step solution

Why the other options are wrong

• (2) Compares the maximum with a single resistor, (20)/2 = 10, instead of with the minimum. All ten in parallel give R/n = 0.2 Ω, so the ratio is n² = 100.
• (3) No single slip produces 2.5. Sanity check: Rₘₐₓ = 20 Ω and Rₘᵢₙ = 0.2 Ω, and (20)/(0.2) = 100.
• (4) No single slip produces 25. Sanity check: the ratio n² does not depend on the value of each resistor, and with n = 10 it is 100.

Reading this solution needs no sign-in. You only sign in to practise against the clock and keep your progress.