## Wednesday, April 6, 2011

### Some more questions posted by visitors

1. if the earth stop rotating about its axis how will be the acceleration due to gravity will be changed.
2. it is easier to swim in sea water,why?
3. freely falling raindrops do not acquire very high velocity why?

### Some Questions from Electrostatics posted by visitors

1. An infinite no. of charges each equal to 4 micro coulomb are place along the x-axis at x=1m,2m,4m and so on.find the electric field at the origin due to given sets of charges.

2. What is meant by a cavity and what is the electric field on the circumference of a cavity whose centre is at a distance 'a' from the centre of a positively charged sphere of radius 'r' and 'rho' volume charge density?

3. when a steady current flows through a conductor, the electron in it move with a certain drift speed which can be calculated for a typical copper wire carrying a small current ( ~ 1 mm/s) which is very small. How is it then that an electric bulb lights up as soon as we turn the switch on?  Please explain

http://plustwophysics.com/differences-between-mass-and-charge/

### Differences between mass and charge

1. Charge is of two types, mass is only of one kind

2. There are two types of forces (attraction and repulsion) between charges, but there is only one kind (attraction) between masses

3. Charge is quantized, but quantization of mass is not established so far

4. Charge has SI unit coulomb, the SI unit of mass is kg

5. Charge is conserved, but mass alone is not conserved (Mass + Energy is conserved)

6. Charge cannot exist without a mass, but mass can exist without a net charge

(... Try finding out more)