Chapter 21.2, Problem 48SSC

To determine

To Explain:The charge buildup on the metal dome of the Van de Graaff generator and the reason for the charge to not repel back onto the belt at point B.

Explanation of Solution

Introduction:

A Van de Graaff generator is a device which produces very high voltage by using static electricity. Static electricity is the result of induction which is the interaction between positive and negative charges. Same charges repel each other while opposite charge attract each other.

The Van de Graaff generator accumulates positive charge on the dome by separating the negative charge from the positive charge. The belt rubbing on the motor develops negative charge on the outside which travels on the belt as it rotates. A grounded metallic comb discharges the negative charge so the belt becomes more positively charged. As the belt rotates further, another comb connected to the metal dome drains the negative charges of the dome onto the more positive charged belt as opposite charges attract. Hence, as the process repeats, the dome becomes highly positively charged.

The charges are not repelled back to the belt at point B because the dome produces no electric field inside it and the induced charges get distributed on the dome.

Conclusion:

The charges are not repelled back to the belt at point B because the dome produces no electric field inside it and the induced charges get distributed on the dome.