A galvanometer has a 50 division scale. Battery has no internal resistance. It is found that there is deflection of 40 divisions when R = 2400 Ω. Deflection becomes 20 divisions when resistance taken from resistance box is 4900 Ω. Then we can conclude:
current sensitivity of galvanometer is 20µA/division
resistance required on R.B. for a deflection of 10 divisions is 9800 Ω.