A property of matter which gives rise to electricity is called charge. The branch of electricity that deals with stationary charges or relatively slow moving charges is known as electrostatics. Static electricity comes under electrostatics.
Charge is of two types; positive charge and negative charge. Like charges repel each other while unlike charges attract each other. Charges are developed on any two different non-conducting objects, when they are rubbed against each other. The electrical charges generated by rubbing are static.
An atom is electrically neutral, or uncharged. If two bodies are rubbed against each other, the free electrons of one body get transferred to the other body. Free electrons are responsible for the electrification of a body. Electrification can be of two types: Positive and Negative. If a body has a less number of electrons as compared to the number of protons in its nucleus, then the body is said to be positively charged. If a body has a more number of electrons as compared to the number of protons in its nucleus, then the body is said to be negatively charged.
Conductors have a large number of free electrons. Insulators have a very few number of free electrons. The free electrons inside a conductor move about randomly. The free electrons flow in a particular direction when a conductor is connected to a source of electricity. The direction of conventional current is opposite to the direction of the flow of electrons.
The neutral objects can be charged by different methods such as charging by friction or rubbing, charging by conduction and charging by induction. An electroscope is a device which is used for detecting whether a body is charged or not. There are two kinds of electroscopes; Gold-leaf electroscope and Pith Ball electroscope.
The phenomenon of charging by rubbing is also observed in atmosphere, is known as lightning. The lightning occurs due to massive electric charge flowing from cloud to cloud, from one part of the cloud to another or from cloud to the ground. To protect buildings from lightning damages, lightning conductor is installed in them. The concept that charge leaks from the pointed ends of a conductor is used in designing the lighting conductor.
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