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A parallel plate capacitor having plates of area S and plate separation d, has capacitance C 1 in air. When two dielectrics of different relative permittivities ( ε 1 = 2 and ε 2 = 4) are introduced between the two plates as shown in the figure, the capacitance becomes C 2 . The ratio 1 2 C C is S/2 S/2 ε 1 ε 2 d / 2 d + –

1. 6/5
2. 5/3
3. 7/5
4. 7/3

Correct answer: 7/3

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