According to Coulomb's Law, what happens to the electric force if a dielectric medium (like glass or water) is introduced between two point charges? MCQ with Answer and Explanation
According to Coulomb's Law, what happens to the electric force if a dielectric medium (like glass or water) is introduced between two point charges?
A. The force decreases.
B. The force remains identical.
C. The force increases.
D. The force drops immediately to zero.
Answer: Option A
Solution (By JKExamLibrary)
Coulomb's force in a vacuum is F = (1/4piepsilon_0) * (q1q2/r^2). When a dielectric medium with relative permittivity (dielectric constant) 'K' is introduced, the new force is F' = F / K. Since K > 1 for all insulating materials (e.g., K for water is ~80), the electrostatic force between the charges is significantly reduced by the medium.
Explanation:
a ∝ -x; magnitude maximum when |x| maximum (extremes). At mean position x=0 ⇒ a=0. Velocity maximum at mean position. Memory aid: 'SHM: a max at extremes, v max at center'. Oscillation concept frequently tested in competitive exams to verify SHM characteristics understanding.
Explanation:
Refractive index n = c/v, where c = 3×10⁸ m/s (vacuum speed). Thus v = c/n = 3×10⁸ / 1.5 = 2×10⁸ m/s. This direct calculation tests optics fundamentals. Memory aid: 'Higher n ⇒ slower light; v = c/n'. Competitive exams frequently test this with common refractive indices. Always use c = 3×10⁸ m/s unless specified; verify units (m/s). This problem assesses basic formula application skills essential for wave optics sections.
Explanation:
Rectifier (diode bridge) converts AC to DC. Inverter DC to AC. Transformer changes AC voltage level. Oscillator generates AC signal. Electronic devices often need DC.
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