Chapter 25 Flashcards
(15 cards)
A capacitor stores charge Q at a potential difference V.What happens if the voltage applied to the capacitor bya battery is doubled to 2 V?
(a) The capacitance falls to half its initial value, and thecharge remains the same.
(b) The capacitance and the charge both fall to half theirinitial values.
(c) The capacitance and the charge both double.
(d) The capacitance remains the same, and the charge doubles.
d (the capacitance is constant)
Many computer keyboard buttons are constructed ofcapacitors as shown in the figure. When a key is pusheddown, the soft insulator between the movable plate andthe fixed plate is compressed. When the key is pressed,what happens to the capacitance?
(a) It increases.
(b) It decreases.
(c) It changes in a way youcannot determine becausethe electric circuit connectedto the keyboard button maycause a change in V.
a
Two capacitors are identical. They can be connected inseries or in parallel. If you want the smallest equivalentcapacitance for the combination,how should you connect them?
in series
You have three capacitors and a battery. In which of the following combinations of the three capacitors is the maximum possible energy stored when the combination is attached to the battery?
in prallel (capacitance needs to be beeeeg)
If you have ever tried to hang a pictureor a mirror, you know it can bedifficult to locate a wooden stud inwhich to anchor your nail or screw. Acarpenter’s stud finder is a capacitorwith its plates arranged side by sideinstead of facing each other as shownin the figure. When the device ismoved over a stud, does thecapacitance(a) increase or(b) decrease?
increase
A fully charged parallel-plate capacitor remains connected to a battery while you slide a dielectric between the plates. What happens to the value of C?
1. It increases.
2. It decreases.
3. It stays the same.
1
A fully charged parallel-plate capacitor remains connected to a battery while you slide a dielectric between the plates. What happens to the value of Q?
1. It increases.
2. It decreases.
3. It stays the same.
1
A fully charged parallel-plate capacitor remainsconnected to a battery while you slide a dielectricbetween the plates. What happens to the value of ΔV?
1. It increases.
2. It decreases.
3. It stays the same.
3
fully charged parallel-plate capacitor remains connected to a battery while you slide a dielectric between the plates. What happens to the value of the energy stored in the capacitor?
1. It increases.
2. It decreases.
3. It stays the same.
1
A parallel-plate capacitor is connected to a battery. What happens to the stored energy if the plate separation is doubled while the capacitor remains connected to the battery?
1. It remains the same.
2. It is doubled.
3. It decreases by a factor of 2.
4. It decreases by a factor of 4.
5. It increases by a factor of 4.
3
If three unequal capacitors, initially uncharged, are connected in series across a battery, which of the following statements is true?
1. The equivalent capacitance is greater than any of the individual capacitances.
2. The largest voltage appears across the smallest capacitance.
3. The largest voltage appears across the largest capacitance.
4. The capacitor with the largest capacitance has the greatest charge.
5. The capacitor with the smallest capacitance has the smallest charge.
2
A capacitor with very large capacitance is in series withanother capacitor with very small capacitance. What isthe equivalent capacitance of the combination?
1. slightly greater than the capacitance of the largecapacitor
2. slightly less than the capacitance of the largecapacitor
3. slightly greater than the capacitance of the smallcapacitor
4. slightly less than the capacitance of the smallcapacitor
4
A parallel-plate capacitor filled with air carries a chargeQ. The battery is disconnected, and a slab of materialwith dielectric constant = 2 is inserted between theplates. Which of the following statements is true?
1. The voltage across the capacitor decreases by afactor of 2.
2. The voltage across the capacitor is doubled.
3. The charge on the plates is doubled.
4. The charge on the plates decreases by a factor of 2.
5. The electric field is doubled.
1
True or False? From the definition of capacitance C =Q/ΔV, it follows that an uncharged capacitor has acapacitance of zero.
false
True or False? As described by the definition ofcapacitance C = Q/ΔV, it follows that the potentialdifference across an uncharged capacitor is zero
true
