16.3. Capacitance http://www.ck12.org
Do not get confused in thinking that the capacitor has twice( 2 Q)the amount of charge since each plate has chargeQ.
The battery has transferred electrons (amounting to chargeQ) from the positive plate of the capacitor to the negative
plate of the capacitor. The total charge of the capacitor is actually zero. The “charged” capacitor, is, technically,
neutral.
b. What is the electric field between the plates of the capacitor?
Answer:
V=Ex→E=9. 00 V
1. 00 × 10 −^3 m= 9 , 000
V
mCapacitors
If you open the back of almost any electronic device, you’re bound to see numerous capacitors.Figure16.9,Figure
16.10, andFigure16.11 show some of the common commercial capacitors. Capacitors are very useful components
in the electronic circuits. They are able to store and release energy innumerable times during their working lifetime.
You may wonder why it is important to do so. By storing charge, voltage differences can be sustained in computers.
Voltage differences mean a computer can store information digitally in the form of zeros and ones.
FIGURE 16.9
Large capacitors.A capacitor in a camera can control the discharge of electricity, providing the characteristic light flash or “electrical
spark.”
Most timing circuits make use of the stored charge (and discharge) in a capacitor. A device that can discharge at
various rates is well suited for such a task.
It is not uncommon to see the power light remain on after an electronic device is shut down. Stored charge on
electronic components does not instantly disappear. Just as inertia always exists, there is always a capacitance in
electronic circuits.
Your teacher may show you a demonstration where a light-emitting diode (LED) is connected to a capacitor that was
charged by a battery. The capacitor lights the LED as it discharges through it. In this instance, a capacitor functions
like a battery.