NEETPhysicsMagnetic Effects of Current
A toroid with a mean radius of 20 cm has 4000 turns of wire wound on its core. If a steady current of 5 A is passed through the wire, what is the magnetic field inside the core of the toroid?
Options
- A2 10⁻⁴ T
- B2.51 10⁻² T
- C0.2 T
- D2 10⁻² T
Correct answer
D. 2 10⁻² T
Step-by-step solution
Mean radius of the toroid, R = 20 cm = 0.2 m Total number of turns, N = 4000 Current, I = 5 A The magnetic field inside the core of a toroid is given by B = ₀ n I , where n is the number of turns per unit length. For a toroid, the length is its mean circumference, so n = N 2 R . Substituting this into the formula gives: B = ₀ N I 2 R B = 4 10⁻⁷ 4000 5 2 0.2 B = 2 10⁻⁷ 20000 0.2 B = 4 10⁻³ 0.2 = 20 10⁻³ T = 2 10⁻² T Answer: 2 10⁻² T