Q149 / 160 · AP EAMCET 2024 (22 May Shift 1) · Physics

Two toroids with number of turns 400 and 200 have arrange radii respectively 30 cm and 60 cm . If they carry the same current, the ratio of magnetic fields in these two toroids is

  • A
    2:1
  • B
    1:4
  • C
    2:3
  • Correct answer
    D
    4:1

Solution

For toroid, magnetic field inside it is $\begin{aligned} & B=\mu_0\left(\frac{N}{2 \pi R}\right) \cdot I \Rightarrow B \propto \frac{N}{R} \\ & \therefore \frac{B_1}{B_2}=\left(\frac{N_1}{N_2}\right)=\frac{400}{200} \times \frac{60}{30}=4: 1 \end{aligned}$

Hence, the correct answer is option: 'D'.

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