If a glass plate is inserted in between the plate of a capacitor in series with a lighted bulb the brightness of the bulb________________?
Correct answer: B. Brightness increases
- A. Remains same
- B. Brightness increases
- C. Brightness decreases
- D. No light
Explanation
Glass acts as a dielectric, increasing the capacitor's capacitance. Since capacitive reactance Xc = 1/(2πfC), the reactance decreases and the series current increases, so the bulb becomes brighter. The likely wrong choice is a, caused by forgetting that inserting a dielectric changes capacitance.
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About Capacitors
Capacitors store electric charge and energy in an electric field between conductors. Work includes capacitance, the relation Q = CV, dielectric materials, charging and discharging, energy formulas, and combinations of capacitors in series and parallel. Electric potential difference is needed to understand why charge and stored energy change.
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