11Ans 2) Gravitational forces are attractive forces whereas Electrostatic forces may be repulsive / attractive. People are bound to earth bcoz gravitational forces are attractive.
There are two kind of charges but only one kind of mass.
hey guyes please help me out
i have lot of conceptual confusions in electrostatics.
1. A charged rod attracts bits of paper due to polarizationin paer molecules but why they often jump violently away from it when touched by the rod .
please explain.
2. how do we know that electro static forces are not the cause of gravitational attraction -b/w earth and moon or b/w us and earth.
3.if the electrons in a metal such as copper are free to move ,they must be headed towards the metal surface. why do they not keep on going and leave
the metal.
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6 Answers
49well i will tr to answer these!
1)
the rod is charged...say it has positive charge...
then....
what it does is, when it finds paper nearby, which was initially electrically neutral, it induces a negative charge in the nearer part and positive charge in the farther end...
as a result there is a net attractive force on the paper and it is attracted
but when the paper comes in contact with the charged rod, a bit of positive charge flows into the paper...and so the paper as a whole becomes a positively charged entity and it gets repelled by the positively charged rod!
i know that 2 positively charged bodies CAN attract each other at times, but i am igoring that case in this level until the question is raised! :P
493)
Tilll the time the electrons remain in the metals, there is no net charge developed in the metal...
now as soon as an electron leaves the metal surface, a positive charge will appear in the metal which will attract the electron and thus there will be creation of potential energy in the system
but as we know energy cannot get created from no-where and is conserved, the case of an electron dumping the metal for something else is out of question until we provide energy from outside to it
and when the energy provided is in the form of light the process of electron release is called photoelectric effect
when electrons are released due to application of heat, it is called thermionic emmission!
11492) for this question i have different views..
invariably the force is not purely gravitational
but the force is resultant of all the interactive forces possible
like electrostatic gravitational magnetic and shayad many more abt which I/We are unaware of! :)
but the thing is gravitational force for the system is more than the other forces and it predominates and thus we consider only forces of gravitation!
12) answer is simple because gravtational forces are long range forces....