Question

A galvanometer has a resistance of 100 Ω and its full scale deflection current is 0.2 mA, what resistance should be added to it to have a range of 0-10 V?

Answer 1

where:

V = 10V = (desired voltage range),

I = 0.2 mA = 0.0002 A (full-scale deflection current),

Rg = 100Ω (internal resistance of the galvanometer),

R is the required series resistance.

Step 1: Calculate the total resistance needed

`R_"total" = V/I = 10/0.0002 = 50000 Ω = 50k Ω` 

Step 2: Find the additional resistance required

`R_"added" = R_"total" − R_g = 50000 − 100 = 49900 Ω = 49.9 kΩ`