| | Classical capacitors made in standard ways of standard materials (such as metal foils) typically have very small electric capacitances (in the range of one millionth to one trillionth of one Farad). On the other hand, capacitors made of new materials can have capacitances up to several tens of Farads. Such capacitors are called super-capacitors. In the diagram in Figure 1, the voltage across such a super-capacitor during discharging through a simple circuit is shown.
Interpretation Note the strong similarity between the behavior of the supercapacitor and that of the chain of capacitors in Figure 2 in the graph on the right. On the other hand, note that the discharge curve is noticeably different from that of a standard capacitor which leads to simple exponential decay as in Figure 3 (graph at the center). Analogy suggests that in the case of a supercapacitor, charge has to diffuse out of the material that stores charge, just like through a chain of capacitors and resistors. A standard capacitor, on the other hand, stores charge only at the surface of a metal sheet from which the charge “drains” without delay, leading to the behavior known from draining a single tank through a pipe at the bottom. | Figure 1
Figure 2
Figure 3
Investigation 13 |
