NTA Abhyas 2020
- Exam
- NTA Abhyas
- Year
- 2020
- Subject
- Physics
- Chapter
- Experimental Physics
NTA Abhyas 2020 · Physics · Experimental Physics
Two tangent galvanometers A and B have coils of radii 8 cm and 16...
Two tangent galvanometers A and B have coils of radii 8 cm and 16 cm respectively and resistance 8Ω 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 ° and60 ° 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 = \dfrac{2r{B}_{H}}{{μ}_{0}N}tan θ.. \left(i\right)
From Eq. (i), we get
\dfrac{rtan θ}{N} = \dfrac{{μ}_{0}I}{2{B}_{H}} = \text{same for both}
∴ \dfrac{{r}_{A}tan {θ}_{A}}{{N}_{A}} = \dfrac{{r}_{B}tan {θ}_{B}}{{N}_{B}}
→
∴ {N}_{B} = 12turns
I = \dfrac{2r{B}_{H}}{{μ}_{0}N}tan θ.. \left(i\right)
From Eq. (i), we get
\dfrac{rtan θ}{N} = \dfrac{{μ}_{0}I}{2{B}_{H}} = \text{same for both}
∴ \dfrac{{r}_{A}tan {θ}_{A}}{{N}_{A}} = \dfrac{{r}_{B}tan {θ}_{B}}{{N}_{B}}
→
∴ {N}_{B} = 12turns