Two equal negative charge -q are fixed at the point (0,a) & (0,-a) on yhe y-axis. a positive charge Q is released from rest at the point (2a,0) on the x-axis. the charge Q will execute oscillatory motion how?
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the capacity of parallel plate condenser is 5 micro Faraday. When a glass plate is placed between the plates of the conductor its potential become 1/8th of the original value. The value of dielectric constant will be
The charge remains same
Why there is a 4π in Coulomb’s law?
Asked Rick Ghosh
This is a consequence of geometry.
Please remember that Coulomb’s law is stated originally for point charges at rest. By symmetry, a point charge should exert equal force on a test charge at all points equidistant from it, which constitute a spherical shell of surface area 4πr2.
This consideration itself suggests the inverse square relation ship as well as the need for 4π.
That was actually my explanation for it.
The term 4π was not there when Coulomb’s law was first stated in cgs system. The term 4π was introduced in SI on rationalization of units based on Maxwell’s equations of electromagnetism.
But I feel that my earlier explanation is simple and convincing.
Hope you got it.
Further discussions are welcome.
What will happen to the size of the soap bubble if the bubble is given charges ?
Asked VARSHA UDAYAKUMAR
Answer: When a soap bubble is charged, its size increases.
Under normal condictions, a soap bubble is in equilibrium un der two opposing forces – the force of surface tension which tries to compress it and the force due to excess pressure which tries to expand it.
When charged, the force of repulsion among the like charges will try to expand the soap bubble further resulting in an increase in size of the bubble.