AIIMS2019Physics-Electrostatics

AIIMS 2019 Physics Forces between charges MCQ Question

Type: MCQ-conceptual-Medium-Class 12

If two protons are moving with speed v = 4.5×10⁵ m/s parallel to each other then the ratio of electrostatic and magnetic force between them

A

4.5×10⁵

B

2.2×10⁵

C

3.3×10⁵

Correct Answer

Option A

Detailed Explanation

The ratio of the electrostatic force (Fₑ) to the magnetic force (Fₘ) between two protons moving parallel to each other can be derived from Coulomb's law and the Biot-Savart law. The electrostatic force is given by Fe=ke2r2Fₑ = \frac{k \cdot e^2}{r^2}, where kk is Coulomb's constant and ee is the charge of the proton, while the magnetic force is Fm=μ04πe2v2r2Fₘ = \frac{μ₀}{4π} \cdot \frac{e^2 v^2}{r^2} for two moving charges. The ratio FeFm\frac{Fₑ}{Fₘ} simplifies to vc\frac{v}{c}, where cc is the speed of light, leading to a numerical value of approximately 4.5×1054.5 \times 10^5 when substituting v=4.5×105m/sv = 4.5 \times 10^5 \, \text{m/s}. Other options do not match this calculated ratio, making them incorrect.

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