physics 118

You hold a negatively charged glass rod near the metal bulb of a neutral electroscope, and then remove it. What happens to the leaves of the electroscope when the rod is removed?

A

A conductor differs from an insulator in that a conductor ________. a. has an excess of protons b. has an excess of electrons c. can become charged and an insulator cannot d. has faster moving molecules e. does not have any neutrons to get in the way of electron flow f. none of these

Answer: F A and B are characteristic of positive and negative objects. As for C, both insulators and conductors can be charged. As for D, this has nothing to do with the conductive properties of materials. As for E, neutrons are located in the nucleus and are "out of the way" of mobile electrons.

5. When an oil tanker car has arrived at its destination, it prepares to empty its fuel into a reservoir or tank. Part of the preparation involves connecting the body of the tanker car with a metal wire to the ground. Suggest a reason for why is this done.

As fuel is pumped from the tanker car to a reservoir, charge can quickly build up as the fluid flows through the hoses. This static charge can create sparks capable of igniting the fuel. By connecting the body of the tanker car to the ground, the static charge can be transferred to the ground. A metal wire is used since metals are conductive and allow charge to flow through them.

You hold a positively charged glass rod near the metal bulb of a neutral electroscope, but don't touch it. What happens to the leaves of the electroscope when the rod is removed? A) the leaves are negatively charged and repel each other. B) the leaves are neutral and collapse. C) the leaves are positively charged and repel each other.

B.

You hold a positively charged glass rod near the metal bulb of a neutral electroscope, and then touch it. What happens to the leaves of the electroscope when the rod is removed? A) the leaves are negatively charged and repel each other. B) the leaves are neutral and collapse. C) the leaves are positively charged and repel each other.

C

4. Suppose that a conducting sphere is charged positively by some method. The charge is initially deposited on the left side of the sphere. Yet because the object is conductive, the charge spreads uniformly throughout the surface of the sphere. The uniform distribution of charge is explained by the fact that ____. a. the charged atoms at the location of charge move throughout the surface of the sphere b. the excess protons move from the location of charge to the rest of the sphere c. excess electrons from the rest of the sphere are attracted towards the excess protons

Check your understanding answer Answer: C Rule out A since atoms are not capable of moving within solid spheres. Rule out B since protons are not capable of moving in electrostatic demos. C is the proper explanation since the negative electrons are attracted to the region of positive charge. The electrons migrate towards the left side of the sphere until there is a uniform distribution of positive charge.