A positive point charge q1 creates an electric field of magnitude E1 at a spot located at a distance r1 from the charge. The charge is replaced by another positive point charge q2, which creates a field of magnitude E2 = E1 at a distance of r2 = 2r1. How is q1 related to q2?
Correct answer: A. q2 = 4q1
- A. q2 = 4q1
- B. q2 = 2q1
- C. q2 = 0.5q1
- D. q2 = 0.25q1
Explanation
Formula for E: E = q / 4πɛr2 Since E1 = E2 q1 / 4πɛr12 = q2 / 4πɛr22 q1 / 4πɛr12 = q2 / 4πɛ (2 r1)2 ( r2 = 2r1) q1 / 4πɛr12 = q2 / 16 πɛ r12 q1 / 4 = q2 / 16 q2 = 4q1Hence, A is the correct option
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Electrostatics describes forces between charges through Coulomb's law, electric fields and field intensity, then uses electric potential to measure energy per unit charge. Capacitors store charge and electrical energy, with capacitance depending on geometry and dielectric material, not simply on the amount of charge present.
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