Physics help?

Question

The belt of a Van de Graaf generator carries a surface charge density of 5.0 mC/m². The belt is 0.50 m. wide and moves at 20.0 m/s.

a.What current does it carry?

b. If this charge is raised to a potential of 100.0 kV, what is the minimum power of the motor needed to drive the belt?

I don't understand how to do the question, pls help me, answers with explanations pls, tnx...

Answer 1

a.Current is a rate of charge flow
I=Q/t
Or in this case it is the amount of charge that can be potentially picked up from the surface of area A that has a charge density p as it moves with the speed V

I = surface charge density x area x speed
or
I= p A v


b. Power is a product of current I and potential difference V
P=I V
This will be the min power required considering a 100% motor efficiency.

Calculations are all yours.

Answer 2

Q = I T
(1 Ampere = 1 Coulomb per second)

Energy = Q. V
( You need one Joule of energy to raise one Coulomb of charge by one Volt of potential )

Power = Joules per second.

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Give it a go and if you go wrong someone will help.....