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## Electrical Capacitance **1. Equivalent capacitance between A and B is C = 1 µF** **2. How will the capacitance of the capacitor change if a very thin metal plate is placed at the middle of the two plates of the parallel plate capacitor?** - The capacitance of an air capacitor, C = A / d (A is...

## Electrical Capacitance **1. Equivalent capacitance between A and B is C = 1 µF** **2. How will the capacitance of the capacitor change if a very thin metal plate is placed at the middle of the two plates of the parallel plate capacitor?** - The capacitance of an air capacitor, C = A / d (A is the area and d is the thickness) - Capacitance with a dielectric of thickness t is C₁ = (k A) / (d-t+t/k) - Capacitance will remain unchanged if the metal plate is very small, i.e. t Cs = 4 µF - Effective capacitance of the series group is 4 µF. **b. The charge on each capacitor** - The charge on each capacitor is equal and is equal to 1200 µC, as the charge is the same in a series connection. **c. The potential difference across each capacitor** - V1 = Q/C1 = 1200/4 = 300 volts - V2 = Q/C2 = 1200/8 = 150 volts - V3 = Q/C3 = 1200/12 = 100 volts **d. The net p.d. of the source** - V = V1 + V2 + V3 = 300 + 150 + 100 = 550 V - Net p.d of the source is 550 V. **4. Connected in parallel** - The capacitors from Q.10 are connected in parallel. - The potential difference across the 8 µF capacitor is 150 volts. **a. The effective capacitance of the parallel group** - Cp = C1+C2+C3 = 4 + 8 + 12 = 24 µF. **b. The potential difference across each capacitor** - Since the capacitors are connected in parallel, the potential difference across all of them will be equal to 150 volts. **c. Charge on each capacitor** - Q1 = C1V = 4 x 150 = 600 µC - Q2 = C2V = 8 x 150 = 1200 µC - Q3 = C3V = 12 x 150 = 1800 µC **d. Total charge** - The total charge is Q = Q1+ Q2 + Q3 = (600 + 1200 + 1800) µC = 3600 µC **5. Small identical charged liquid drops** - n small identical charged liquid drops coalesce to form a large drop. - Q, V, and C are the charge, potential, and capacity of each small drop. - Qy, Vy, and Cy are the charge, potential, and capacity of the large drop - Potential and Capacity of the large drop can be found depending on the number of these small drops.