Explain the source of energy for charging the battery of an automobile.

Figure 1- Car generator (Used with permission from © INSADCO Photography/Alamy.)
and battery charging circuit. 

The battery is charged by the car itself. In the engine, the chemical energy of the fuel is converted into mechanical energy (rotary motion) available at the crankshaft. This is delivered to the input of the alternator using a fan belt. The shaft of the alternator has a cylindrical structure and has electric conductors on its periphery attached to it. Thus, it forms the rotor of the car’s generator. The rotary movement at the input causes the rotor to move, and therefore, the conductors cut the magnetic flux present inside the alternator, and electricity is generated. This electrical energy is fed to rectifiers that convert alternating (time varying) voltage at the alternator to constant (DC) voltage required to charge the battery.  Figure  1 represents the car generator structure and the circuit for charging the battery. 

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Explain the application of storage batteries.

Storage batteries are used for various purposes, some of the applications are mentioned below:

• For the operation of protective devices and for emergency lighting at generating stations and substations.

• For starting, ignition and lighting of automobiles, aircrafts etc.

• For lighting on steam and diesel railways trains.

• As a supply power source in telephone exchange, laboratories and broad casting stations.

• For emergency lighting at hospitals, banks, rural areas where electricity supplies are not possible.

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What is the difference between a battery and a capacitor?

While batteries and capacitors have similarities, there are several key differences. Like -

• Electrical energy in a Capacitor is stored in an electric field, where a Battery stores its electrical energy in a chemical form. 

• When a battery is discharging it, can be slower than a capacitor's ability to discharge because there is a latency associated with the chemical reaction to transfer the chemical energy into electrical energy. A capacitor is storing the electrical energy directly on the plates so discharging rate for capacitors are directly related to the conduction capabilities of the capacitor plates. 

• A capacitor is able to discharge and charge faster than a battery because of this energy storage method also. But unlike a battery that can turn its electrical current on and off, once a capacitor is connected to an outside circuit it will discharge as fast as it can until all the charge is drained. 

• Capacitors are much larger than a battery that stores equivalent charge. 

• The battery runs for longer time, but a capacitor discharges almost instantaneously. 

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