A long straight current-carrying wire produces a magnetic field of magnitude 2 × 10⁻⁴ Wb/m² at a perpendicular distance of 5 cm. An electron at the same location moves at 10⁷ m/s towards the wire, perpendicular to it. Find the magnetic force on the electron (e = 1.6 × 10⁻¹⁹ C).
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Question

A long straight current-carrying wire produces a magnetic field of magnitude 2 × 10⁻⁴ Wb/m² at a perpendicular distance of 5 cm. An electron at the same location moves at 10⁷ m/s towards the wire, perpendicular to it. Find the magnetic force on the electron (e = 1.6 × 10⁻¹⁹ C).

Options

G1 Physics · Accepted Answer

Step 1: Magnetic field lines circulate around the wire; radial electron velocity is perpendicular to B. Step 2: F = evB sin90°. Step 3: F = (1.6 × 10⁻¹⁹)(10⁷)(2 × 10⁻⁴) = 3.2 × 10⁻¹⁶ N. Correct option B. Final answer: (B) 3.2 × 10⁻¹⁶ N.