A parallel plate capacitor with air has capacitance C. If a dielectric (εr= 2) fills half the gap between plates, the new capacitance is:
Correct answer: D. 4C/3
- A. 1.5C
- B. 2C
- C. C
- D. 4C/3
Explanation
The system acts as two capacitors in parallel: one with air (C₁ = ε₀A/(2d)) and one with dielectric (C₂ = 2ε₀A/(2d)). Total C = C₁ + C₂ = (ε₀A/(2d)) + (2ε₀A/(2d)) = (3/2)(ε₀A/d) = (3/2)C/2 = 4C/3.
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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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