CBSEGrade 12PhysicsElectrostatic Potential and Capacitance

Combination of Capacitors?

Three capacitors of capacitances 2 μF, 3 μF and 5 μF are connected in parallel across a 20 V battery. How will the total capacitance of the combination be affected if a dielectric material of dielectric constant 3 is inserted between the plates of the 2 μF capacitor?

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📌 CONCEPT: When capacitors are connected in parallel, the total capacitance is the sum of individual capacitances, and if a dielectric material is inserted between the plates of one capacitor, its capacitance increases by a factor of the dielectric constant.

📐 RULE / FORMULA: The total capacitance (C_total) of capacitors connected in parallel is given by the formula C_total = C_1 + C_2 +... + C_n, and the capacitance of a capacitor with a dielectric material is given by C = ε_0 * ε_r * C_0, where ε_r is the dielectric constant.

💡 WORKED EXAMPLE: Initially, the total capacitance of the combination is 2 μF + 3 μF + 5 μF = 10 μF. If a dielectric material of dielectric constant 3 is inserted between the plates of the 2 μF capacitor, its new capacitance will be 2 μF * 3 = 6 μF. Now, the total capacitance will be 6 μF + 3 μF + 5 μF = 14 μF.

⚠️ COMMON MISTAKE: Students often forget to consider the effect of inserting a dielectric material on the capacitance of the capacitor it is inserted into, and only calculate the total capacitance without accounting for the increase in capacitance of that particular capacitor.

13 Jul 26