KCET2007PhysicsCurrent Electricity
Two tangent galvanometers A and B have coils of radii 8 ~cm and 16 ~cm respectively and resistance 8 each. They are connected in parallel with a cell of emf 4 ~V and negligible internal resistance. The deflections produced in the tangent galvanometers A and B are 30° and 60° respectively. If A has 2 turns, then B must have
Options
- A18 turns
- B12 turns
- C6 turns
- D2 turns
Correct answer
B. 12 turns
Step-by-step solution
Current in tangent galvanometer I= 2 r H ₀ N Here, R₁ and R₂ are in parallel 1 R_ n e t = 1 R₁ + 1 R₂ = R₂+R₁ R₁ R₂ = 8+8 8 8 R_ n e t =4 Hence, I= V R = 4 4 =1 ~A From Eq. (i), we get aligned r N &= ₀ I 2 H r_ A _ A N_ A &= r_ B _ B N_ B 8 1 3 2 &= 16 3 N_ B N B &=12 turns aligned