An infinitely long straight conductor carries a current of 5 A. An electron moves parallel to it at speed 10⁵ m/s. At the instant shown it is 20 cm from the conductor. Calculate the magnitude of magnetic force on the electron. [Image]
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Question

An infinitely long straight conductor carries a current of 5 A. An electron moves parallel to it at speed 10⁵ m/s. At the instant shown it is 20 cm from the conductor. Calculate the magnitude of magnetic force on the electron. [Image]

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G1 Physics · Accepted Answer

Step 1: Magnetic field at perpendicular distance r from a long straight wire is B = μ₀I/(2πr). Step 2: Given I = 5 A and r = 20 cm = 0.20 m, B = (4π × 10⁻⁷ × 5)/(2π × 0.20) = 5 × 10⁻⁶ T. Step 3: The electron moves perpendicular to the circular magnetic field, so |F| = e v B. Step 4: |F| = (1.6 × 10⁻¹⁹ C)(10⁵ m/s)(5 × 10⁻⁶ T) = 8 × 10⁻²⁰ N. Final answer: (D) 8 × 10⁻²⁰ N.