Category Physics

          Initially, direct current was used for power transmission. It was only in the 1950s that people realized the merits of alternating current over the other.

          Although the two are used today, alternating current is more accepted worldwide. It is used for bigger appliances as well as in houses. Let us see why.

          One of the main reasons for having AC for domestic purposes is that it causes very low wastage of power. It is seen that even at high voltages above 110 KV, less energy is lost in transmission. Yet another peculiarity of AC electricity is that voltage can easily be changed from high voltage to low and vice versa. This in turn makes it suitable for long distance transmission, unlike DC.

            Alternating current is also known to be capable of powering electric motors. Thus, it is useful for high-end appliances like refrigerators, televisions, computers etc.

            In terms of safety too, AC is preferred to DC power.

            It is for these reasons that most countries in the world favour AC than DC power. 

         Batteries can be broadly divided into two – primary and secondary.

         Primary batteries are single-use batteries – that are they can be used only once. After that, they should be discarded. They cannot be recharged. Quite a few non-rechargeable batteries are used in our daily life. This includes batteries used in toys, radios, remote controls, flashlights, clocks etc.

         Those batteries that can be recharged and reused are called secondary batteries. Through electric current, these batteries can be recharged.

         Secondary batteries can be seen in many devices including cell-phones, MP3 players etc.

         Yet another example can be seen in cars and trucks. Did you know that there is a lead-acid battery that works every time we start a car? This is how the car gets energy to run the lights and radio when the engine is not running. The battery in the car is recharged while we drive.

         Besides lead-acid, there are other batteries that can be recharged. This includes the nickel-cadmium battery, lithium-ion battery, nickel-metal hydride batteries etc.

          A battery is a device that stores electricity in chemical form inside a closed-energy system.

          Long before the invention of electrical generators and grids batteries proved to be the main source of electricity, and still continue to serve this purpose.

          There are batteries in different shapes. Some are very small, like the ones used in wristwatches, or smart phones, and some are as big as those used in cars and trucks. At the extreme, there are huge battery banks that are the size of rooms.

           All batteries have three parts- an anode (the negative side), a cathode (positive side) and an electrolyte, a liquid or gel that contains electrically charged particles called ions.

          When connected to an external circuit, the ions interact with the other two, and a chemical reaction takes place inside the battery.

          This reaction results in the generation of electric current. This is how batteries function and provide electric power to all appliances in our house including mobile, phones, laptops, flashlights etc.

           Batteries are devices that have been helping mankind for a long time. But nobody knows exactly when they were invented.

         An account of the earliest battery came in 1938 from Baghdad. The story goes that while constructing a railway line in the city, workers uncovered a pre-historic battery. Experts said that the battery belonged to the Parthian Empire, and was at least 2000 years old!

         Luigi Galvani, in 1786, was conducting an experiment when he accidentally touched a dead frog’s legs with two different metals. Suddenly the muscles of its legs contracted. He thought it was because of ‘animal electricity’. But his friend and fellow scientist Alessandro Volta didn’t agree. He guessed that the same effect would be produced if cardboard was soaked in salt water, instead of a frog’s leg. So, he stacked copper and zinc discs, separated by a cloth, and soaked them in salt water. He connected wires to either end of the stack.

                To his surprise, it produced stable current. Thus in 1800, Volta invented the ‘voltaic pile’, the first true battery that produced continuous and stable current. This is believed to have laid the foundation for the modern battery. 

           The Daniell cell is perhaps the first practical purpose battery ever. It was an electrochemical cell developed by the English chemist John Daniell in 1836. The cell offered a long-lasting source of power.

           Let’s see how the cell works. Daniell cell, consist of a copper pot filled with a copper sulfate solution, in which was immersed an unglazed earthenware container filled with sulfuric acid and a zinc electrode. The earthenware barrier which is porous, allows ions to pass through, but keeps the solutions from mixing.

           This cell produces current like a voltaic cell does, but with more efficiency. It soon became the industry standard for use. A voltage of over one volt is produced by a Daniell cell. To get a little more voltage, one has to increase the concentration of the solution in which the electrodes are dipped.

Electromagnetism is a basic force of nature. It is the creation of a magnetic field from the movement of electrical charges.

The basic characteristics of this force can be best defined through the example of a copper wire. When electric current is allowed to pass through the wire, it can attract, or magnetize pieces of iron or steel near it. That is, the electromagnetic force causes the attraction, as well as repulsion, of electrically charged particles.

There are two basic concepts behind electromagnetism. The first one is that, any moving charge produces a magnetic field because of its movement. The second one is that, a moving magnetic field can cause current to flow into a conducting loop. This means, if there is a moving bar magnet near a coil of wire that is connected to a meter, it can detect the current flow.