# Working with charges and their potential.

1>What is the electric potential at a point 0.45 m away from a point charge of a of 2.5mC

2> If 3.75 X 10^-4 J of work are required to move 13.7 microc of charge from one point to another, what is the electric potentail difference the two points.

3> An electron is released from rest in a vacumm between two flat, parallel metal plates that are 10.0 cm apart and are maintained at a constant electric potental difference of 750 V. (a) If the electron is released from the negative plate, what is its speed just before it strikes the positive plate? (b) what is the kinetic energy of the eletron in units of eV?

4> An isolated metal sphere of radius R carries a positive charge of Q. Another isolated metal sphere, initially uncharged and of radius R/2, is brought into contact withthe first sphere, and the teo are then separated. how much change remains on the first sphere?

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#### Solution Preview

The electric potential at point distant r from a point charge is given by the formula

V = (1/4*pi*e0) * q/r = k * q/r

Where k = 8.99 * 10^9 and q is the magnitude of the charge.

Thus we have,

V = 8.99*10^9* 2.5*10^-3C/0.45m

= 4.99 * 10^7 Volt ---Answer

II. You are spending 3.75 X 10^-4 J amount work means, the potential energy of the chrge is increased by that much amount (energy can neither be created nor be destroyed..changes from one form to the other)

Now to the definition of electric potential: The Potential Energy per unit charge at a given location in space

Thus Potential = PE/charge = ...

#### Solution Summary

All questions answered with all proper explanations. A good set of practice solutions.