Question

Two ammeters, one with a full-scale current of 1 mA and internal resistance of 100 Ω and other a full-scale current of 10 mA and internal resistance of 25 Ω are in parallel. What is the total current, these two meters can carry without the reading out of scale in any meter?

(a) 1 mA

(b) 10 mA

(c) 11 mA

(d) 5 mA

This question was addressed to me in an online interview.

My doubt stems from Advanced Problems on Indicating Instruments in division Extension of Instrument Ranges of Electrical Measurements

Answer 1

Right option is (d) 5 mA

To explain I would say: The lower current Il will decide the total current.

∴ T × \(\frac{25}{125}\) = 1 mA

Or, T = 5 mA.