Measuring Electric Field Strength

[GeeUnit]

I have to construct an experiment which measures the electric field strength at various distances from a charged Van Der Graaff generator. How would i go about this?

 

[cragar]

put a piece of iron on the end of a spring , measure the spring constant , then see how much the spring is stretched by the magnetic field created by the generator . F=kx where k is the spring constant and x is the change in length of the spring . Or get a cathode ray tube and shoot electrons out of it and relate it to the Lorentz force ., and relate that to the centripetal force ,