How can nature of charge be detected with the help of an electroscope. pls explain
Electroscopes cannot predict the type of charge without a standard reference. Because of the same magnitudes of the opposite charges and same force of attraction for +ve and –ve charges, it is not possible to detect the type of charge directly.
However, the polarity of charge on an object can be identified by the electroscope, by the following method.
Charge the electroscope by the induction method. A rod of opposite polarity to that required on the electroscope can be used for charging it. The rod is brought near to the cap so that the leaf diverges by the amount desired, and the electroscope is momentarily earthed by touching it with a finger, keeping the rod in position. The rod is then removed, leaving the electroscope charged. (If the charged rod used is ebonite, this leaves a positively charged electroscope, if a glass rod is used then the result is a negatively charged electroscope).
Now bring the object of unknown charge down from a good height and move it slowly towards the cap of the electroscope. A charge of the same kind as that on the electroscope will cause an increase in leaf divergence, while a charge of the opposite kind will cause a decrease in leaf divergence when the object is brought near to the electroscope.
An electroscope is an early scientific instrument that is used to detect the presence and magnitude of electric charge on a body. It was the first electrical measuring instrument. The first electroscope, a pivoted needle called the versorium, was invented by British physician William Gilbert around 1600. The pith-ball electroscope and the gold-leaf electroscope are two classical types of electroscope that are still used in physics education to demonstrate the principles of electrostatics. A type of electroscope is also used in the quartz fiber radiation dosimeter. Electroscopes were used by the Austrian scientist Victor Hess in the discovery of cosmic rays.
Electroscopes detect electric charge by the motion of a test object due to the Coulomb electrostatic force. The electric potential or voltage of an object equals its charge divided by its capacitance, so electroscopes can be regarded as crude voltmeters. The accumulation of enough charge to detect with an electroscope requires hundreds or thousands of volts, so electroscopes are only used with high voltage sources such as static electricity and electrostatic machines. Electroscopes generally give only a rough, qualitative indication of the magnitude of the charge; an instrument that measures charge quantitatively is called an electrometer.
Electroscopes detect electric charge by the motion of a test object due to the Coulomb electrostatic force.Suppose, a known charged body is touched with an electroscpe along wit the unknown charged body to be tested,the charges can be detected by repulsion as like charges repel and unlike charges attract.