Question

1) A negatively charged Teflon (plastic) rod is held near two initially neutral aluminum pie plates that are touching as shown at right. The plates are held using insulating cups. The Teflon rod never touched the pie plates, and no sparks have jumped. Negatively charged Teflon rod a. Is the magnitude of the net charge of the small pie plate greater than, less than, or equal to the magnitude of the net charge of the large pie plate? If the net charge of either plate i:s zero, state so explicitly. Explain your reasoning. Suppose a sweaty person were to touch the small pie plate as shown. Would the net charge of the system consisting of both pie plates be positive, negative, or zero? Explain b. Negatively charged Te flon rod 2) The picture shows the electric field of two charges at point A and point B. a. b. c. Identify the sign of each charge. Compare the magnitude of charges at point A and point B A small negative charge is released from rest from point P. Which way will it start to move? Describe clearly, or copy the drawing and draw an arrow.

Answer 1

a) net charge of either of plate is zero because these plates are neutral. But due to presence of negativity charged teflon electrons and postive charge on these plates are separated inside it ( I.e polarised)

b) when sweaty person touches the small pie plate electron from smaller plate conducts from plate to body of the person so small plate becomes positively charged  

2.

a) charge of B is postive while charge of A is negative, because field lines originated from B and terminates at B.

b) charge at B is greater than charge at A. Because field lines near B is relatively closer.

c) Tangent on point p gives direction of electric field or electric force, and motion of charge is in the direction of electric field.