91影视

When the proton and electron in MisConceptual Question 6 strike the opposite plate, which one has more kinetic energy?

(a) The proton.

(b) The electron.

(c) Both acquire the same kinetic energy.

(d) Neither鈥攖here is no change in kinetic energy.

(e) They both acquire the same kinetic energy but with opposite signs.

If \({\bf{V = 0}}\) at a point in space, must \({\bf{\vec E = 0}}\) ? If \({\bf{\vec E = 0}}\) at some point, must \({\bf{V = 0}}\) at that point? Explain. Give examples for each.

Which of the following do not affect capacitance?

(a) Area of the plates.

(b) Separation of the plates.

(c) Material between the plates.

(d) Charge on the plates.

(e) Energy stored in the capacitor.

Can two equipotential lines cross? Explain.

In the dynamic random access memory (DRAM) of a computer, each memory cell contains a capacitor for charge storage. Each of these cells represents a single binary bit value of 鈥�1鈥� when its 35-fF capacitor \(\left( {{\bf{1}}\;{\bf{fF = 1}}{{\bf{0}}^{{\bf{ - 15}}}}\;{\bf{F}}} \right)\) is charged at 1.5 V, or 鈥�0鈥� when uncharged at 0 V.

(a) When fully charged, how many excess electrons are on a cell capacitor鈥檚 negative plate?

(b) After charge has been placed on a cell capacitor鈥檚 plate, it slowly 鈥渓eaks鈥� off at a rate of about \({\bf{0}}{\bf{.30}}\;{\bf{fC/s}}\). How long does it take for the potential difference across this capacitor to decrease by 2.0% from its fully charged value? (Because of this leakage effect, the charge on a DRAM capacitor is 鈥渞efreshed鈥� many times per second.) Note: A DRAM cell is shown in Fig. 21鈥�29.

A battery establishes a voltage Von a parallel-plate capacitor.After the battery is disconnected, the distance between the plates is doubled without loss of charge. Accordingly,the capacitance _________ and the voltage between theplates _________.

(a) increases; decreases.

(b) decreases; increases.

(c) increases; increases.

(d) decreases; decreases.

(e) stays the same; stays the same.

Draw in a few equipotential lines in Fig. 16鈥�32b and c.

FIGURE 16-32