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JEE Main 2022 (26 Jul, Shift 1) · Dielectrics

Dielectrics question from JEE Main 2022 (26 Jul, Shift 1)

Q66JEE Main 2022 · 26 JUL · SHIFT 1Medium

Dielectrics

A composite parallel plate capacitor is made up of two different dielectric materials with different thickness (t1(t_1 and t2)t_2) as shown in figure. The two different dielectric materials are separated by a conducting foil F\text{F}. The voltage of the conducting foil is ____________ V.

Figure

Numerical answer type. Work it out, then open the answer.

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Answer: 60

  1. The foil splits it into two capacitors in series, C∝εrtC\propto\frac{\varepsilon_r}{t}.
  2. C1∝30.5=6C_1\propto\frac{3}{0.5}=6, C2∝41=4C_2\propto\frac{4}{1}=4; series charge is the same, so V∝1CV\propto\frac{1}{C}.
  3. V1=100×410=40 VV_1=100\times\frac{4}{10}=40\text{ V}, V2=60 VV_2=60\text{ V}
  4. Taking the negative (lower) plate at 0 V, foil potential =V2=60 V=V_2=60\text{ V}
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