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121. Why do the plates of a parallel plate capacitor connected to a battery acquire exactly equal and opposite charges? A parallel plate capacitor consists of conducting plated separated by an insulator called dielectric. When a parallel plate capacitor is connected to a battery (i.e. charged by a battery) then the field between the plates distorts the molecules of the dielectric. The positive nuclei are shifted in the direction of field and negative electrons are shifted in opposite direction. The molecules are hence polarized i.e. the molecules acquire exactly equal & opposite charges. 122. Is the electrostatic potential necessarily be zero at a point where the electric field strength is zero? The electric field strength E is defined as the ratio of change in voltage dV to the change in length dr.
If the electric field strength is zero i.e. E = 0 then relation 1 becomes:
Integrating both sides, we get:
If the electric field strength is zero i.e. E = 0 at a point, the electrostatic potential is not necessarily be zero at that point but the electrostatic potential will be constant according to the relation 2.
123. Is it possible for two balls having same kind of charges on them attracting each other? Explain. Yes, it is possible for two balls having same kind of charges (like charges) on them attracting each other when out of two like charges, one charge contains more electrons and other charge contains less electrons, then there develops a force of attraction between them due to the difference in the electron. The electrons flow from charge containing greater electrons to the other charge and when the electrons in both the charges becomes equal then both the charges remains stationary. 124. A person touching a highly charged sphere has his hair standing on end, why? A person is a good conductor of electricity. As the surface charge density at the pointed end is very high which creates a high electric field in the region close of that pointed end that causes the ionization of air molecules. When a person touches a highly charged sphere, he is positively charged & the negative ions i.e. electrons are attracted to the pointed end i.e. the tip of his hair & neutralize the positive charge in the pointed end. The sphere discharges quickly & at the same time the electric wind is set up on his hair & repulsion of positive ions occurs resulting his hair standing on end. hence, a person touching a highly charged sphere has his hair standing on end. 125. Can two like charges attract each other? Yes, two like charges can attract each other when out of two like charges, one charge contains more electrons and other charge contains less electrons, then there develops a force of attraction between them due to the difference in the electron. The electrons flow from charge containing greater electrons to the other charge and when the electrons in both the charges becomes equal then both the charges remains stationary. |
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