Solve the following:
a)The potential difference across a capacitor is doubled. How does each of the following quantities change: (a) the capacitance; (b)
the stored energy: (c) the stored charge.
b)A parallel-plate capacitor is connected to a battery. Consider what happens as you move the plates closer together.
(a)How are the charge, potential difference, and energy affected?
(b]Would you do positive or negative work in moving the plates?
Answers
Answer:
it iswere long problem
Explanation:
( a )
An ideal capacitor will not change its capacitance versus applied voltage. And many engineers assume that capacitance is independent of applied voltage for all capacitors (as shown by some of the other answers to this question).
An ideal capacitor will not change its capacitance versus applied voltage. And many engineers assume that capacitance is independent of applied voltage for all capacitors (as shown by some of the other answers to this question).However, experienced design engineers know that some types of real-world capacitors undergo significant changes in capacitance as the applied voltage is increased. This behavior is called the "Voltage Coefficient of Capacitance" (VCC). It occurs when the dielectric constant (k) of the capacitor's dielectric changes as a function of the internal electrical field inside the dielectric. VCC for polyester or polypropylene film and mica capacitors is quite small. However, some commonly-used ceramic capacitors (such as EIA types X7R, X5R, and Y5V) can lose up to 60 - 80% of their printed value when operating at their rated DC voltage.
( b )
A capacitor is a device used to store electric charge. Capacitors have applications ranging from filtering static out of radio reception to energy storage in heart defibrillators. Typically, commercial capacitors have two conducting parts close to one another, but not touching, such as those in Figure 1. (Most of the time an insulator is used between the two plates to provide separation—see the discussion on dielectrics below.) When battery terminals are connected to an initially uncharged capacitor, equal amounts of positive and negative charge, +Q and –Q, are separated into its two plates. The capacitor remains neutral overall, but we refer to it as storing a charge Q in this circumstance.