A 20mv, 1mA d’Arsonval movement is used in an ammeter whose full-scale

a-20mv-1ma-darsonval-movement-is-used-in-an-ammeter-whose-full-scale

A 20mv, 1mA d’Arsonval movement is used in an ammeter whose full-scale reading is 10 mA. Determine RA.

A. 2.222Ω

B. 6.667Ω

C. 5.92Ω

D. 3.333Ω

I got this question during an online interview.

I’m obligated to ask this question of Measuring Voltage and Current in chapter Simple Resistive Circuits of Electric Circuits

The correct answer is A. 2.222Ω

To elaborate: 1 mA flowing through coil implies that 9mA must be diverted through RA.

          V = ir

      20 * 10^-3 = 9 * 10^-3 RA

      RA= 2.222Ω.