8.5 Molecular model of a dielectric  (Page 7/13)

A $4.00\text{-}\mu \text{F}$ capacitor and a $6.00\text{-}\mu \text{F}$ capacitor are connected in parallel across a 600-V supply line. (a) Find the charge on each capacitor and voltage across each. (b) The charged capacitors are disconnected from the line and from each other. They are then reconnected to each other with terminals of unlike sign together. Find the final charge on each capacitor and the voltage across each.

Three capacitors having capacitances of 8.40, 8.40, and 4.20 $\text{μ}\text{F}$ , respectively, are connected in series across a 36.0-V potential difference. (a) What is the charge on the $4.20\text{-}\text{μ}\text{F}$ capacitor? (b) The capacitors are disconnected from the potential difference without allowing them to discharge. They are then reconnected in parallel with each other with the positively charged plates connected together. What is the voltage across each capacitor in the parallel combination?

A parallel-plate capacitor with capacitance $5.0\text{μ}\text{F}$ is charged with a 12.0-V battery, after which the battery is disconnected. Determine the minimum work required to increase the separation between the plates by a factor of 3.

(a) How much energy is stored in the electrical fields in the capacitors (in total) shown below? (b) Is this energy equal to the work done by the 400-V source in charging the capacitors?

Three capacitors having capacitances 8.4, 8.4, and 4.2 $\text{μ}\text{F}$ are connected in series across a 36.0-V potential difference. (a) What is the total energy stored in all three capacitors? (b) The capacitors are disconnected from the potential difference without allowing them to discharge. They are then reconnected in parallel with each other with the positively charged plates connected together. What is the total energy now stored in the capacitors?

(a) An $8.00\text{-}\mu \text{F}$ capacitor is connected in parallel to another capacitor, producing a total capacitance of $5.00\mu \text{F}$ . What is the capacitance of the second capacitor? (b) What is unreasonable about this result? (c) Which assumptions are unreasonable or inconsistent?

(a) On a particular day, it takes $9.60\times {10}^3\text{J}$ of electrical energy to start a truck’s engine. Calculate the capacitance of a capacitor that could store that amount of energy at 12.0 V. (b) What is unreasonable about this result? (c) Which assumptions are responsible?

(a) A certain parallel-plate capacitor has plates of area $4.00{\text{m}}^2$ , separated by 0.0100 mm of nylon, and stores 0.170 C of charge. What is the applied voltage? (b) What is unreasonable about this result? (c) Which assumptions are responsible or inconsistent?