Point charge of mass .210kg and net charge +.340uC hangs at rest at the end of an insulating string above a large sheet of charge. The horizontal sheet of uniform charge creates a uniform vertical electric field in the vicinity of the point charge. The tension in the string is measured to be 5.67N calculate the magnitude and direction of the electric field due to the sheet of charge

Question

anonymous · Answer

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experimentx · Answer

tension should normally be 0.21x9.8 N = 2.058N
but the total tension is 5.67N 
so, 5.67N  - 2.058N = 3.612N must be due to attraction caused by the charge.

But we know, F = QE, where E is electric field at the point of charge.

experimentx · Answer

electric field due to infinite large sheet of charge will always be constant, and will be pointed upwards, For more refer http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elesht.html

anonymous · Answer

how do you determine the direction of E?

experimentx · Answer

the direction of E will be along g, since it is being pulled downards.

anonymous · Answer

is it always determined by g? In other problems, I am only given F direction?

experimentx · Answer

no it is always determined by the direction of force ... in this case, in which direction is the electrostatic force felt??

anonymous · Answer

down