Practice question

Given: An electron moves with a speed of 4 × 10⁶ m/s perpendicular to a magnetic field of 0.3 T . What is the radius of its path? (Mass = 9.1 × 10⁻³¹ kg, charge = 1.6 × 10⁻¹⁹ C ) These values define the system as per NCERT data. Formula: Radius r = mv/qB. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: r = frac9.1 × 10⁻³¹ × 4 × 10⁶¹.6 × 10⁻¹⁹ × 0.3 = frac3.64 × 10⁻²⁴⁴.8 × 10⁻²⁰= 7.58 × 10⁻⁵ m = 7.58 × 10⁻³ cm . Result: The computed value matches the expected outcome and confirms the correct choice. Units and powers like J kg⁻¹ K⁻¹, m/s², 10⁻⁵ are properly used as per NCERT.