A long straight wire carrying a current of 30 A is placed in an external uniform magnetic field of induction 4 x 10^-4 T. The magnetic field is acting parallel to the direction of the current. The magnitude of the resultant magnetic induction in tesla at a point 2.0 cm away from the wire is:
Correct answer: C. 5 x 10^-4
- A. 10-4
- B. 3 x 10^-4
- C. 5 x 10^-4
- D. 6 x 10^-4
Explanation
Magnetic field due to wireB = μ₀I / 2πr = (4π × 10⁻⁷) / 2π × 30 / (2 × 10⁻²) = 3 × 10⁻⁴ TThis magnetic field will be perpendicular to external magnetic field.∴ Net magnetic fieldB = √(B² + B₀²) = √[(3 × 10⁻⁴)² + (4 × 10⁻⁴)²] = 5 × 10⁻⁴ T
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