Capacitors vs Batteries

capacitors and batteries are frequently compared because both are energy storage devices however there are fundamental differences among them as we will see both capacitors and batteries have a positive and a negative terminal that provide a potential difference or voltage if we connect a load for example a lamp an electric current will flow but this is where the similarities end first of all batteries store much more energy than capacitors let's compare a 1.5 volt triple-a alkaline battery with a for 700 micro farad capacitor charge at 1.5 volts these two are approximately of the same size while the battery can store a total energy of approximately 5,000 Jews the capacitor can store a total energy of 5 milli Joule that is the battery stores 1 million times more energy than the capacitor another important difference between batteries and capacitors is the way in which the voltage changes with time if we make a plot of voltage versus time for example for a fresh double-a battery that has been never used the initial voltage is around 1 point 65 volts when we start using the battery this voltage will quickly drop to the nominal voltage of 1.5 volts and this value will stay approximately constant throughout the life of the battery when the battery is depleted this voltage will quickly drop until the battery is not not longer useful in a capacitor if we make the same kind of plot voltage versus time and the capacitor is charged to the same 1.5 volts when we start using the energy in the capacitor this voltage will drop continually in time therefore we do not have a range of constant voltage in a capacitor as in the case of the battery we have this range of time when we have approximately the same voltage coming from the battery another difference is the maximum current output batteries and capacitors are non-ideal devices they have an internal resistance that limits the maximum current that they can deliver a double a alkaline battery has an internal resistance of around point 15 ohms since current equals voltage divided by resistance the short-circuit current of the battery will be 10 amperes on the other side capacitors have a much lower internal resistance a 4700 electrolytic capacitor has an internal resistance of only 25 milli ohms this means that they can deliver a current of up to 60 amps of course this 60 amps will circulate only for a very short time much less than a second in the following experiment we will see the effects produced by the high currents that capacitors can deliver here we have a 600-volt 1900 micro farad capacitor I am going to charge it to approximately 250 volts after charging now I'm going to take a piece of aluminum foil and short circuit the capacitor with the foil and let's see what happens William several hundred amps circulate through the foil as we can see we have two holes in the aluminum foil the material has been bubble rise by the extremely high current produced by the capacitor a recent development our super capacitors or ultra capacitors they can store much more energy than normal capacitors they will be the subject of a future video

Channel: Ludic Science

Views: 520,822

Keywords: science, physics, electricity, experiment, homemade, howto, Capacitor (Invention), Battery (Invention), Energy

Id: LNci-13Bp1U

Length: 4min 47sec (287 seconds)

Published: Fri Oct 02 2015