18.1 Static Electricity and Charge: Conservation of Charge

When a glass rod is rubbed against silk, which of the following statements is true?

1. Electrons are removed from the silk.
2. Electrons are removed from the rod.
3. Protons are removed from the silk.
4. Protons are removed from the rod.

If objects X and Y attract each other, which of the following will be false?

1. X has positive charge and Y has negative charge.
2. X has negative charge and Y has positive charge.
3. X and Y both have positive charge.
4. X is neutral and Y has a charge.

What will be the net charge on an object which attracts neutral pieces of paper but repels a negatively charged balloon?

1. negative
2. positive
3. neutral
4. cannot be determined

In an experiment, a student runs a comb through his hair several times and brings it close to small pieces of paper. Which of the following will he observe?

1. Pieces of paper repel the comb.
2. Pieces of paper are attracted to the comb.
3. Some pieces of paper are attracted and some repel the comb.
4. There is no attraction or repulsion between the pieces of paper and the comb.

Suppose an object has a charge of 1 C and gains 6.88×10¹⁸ electrons.

1. What will be the net charge of the object?
2. If the object has gained electrons from a neutral object, what will be the charge on the neutral object?
3. Find and explain the relationship between the total charges of the two objects before and after the transfer.
4. When a third object is brought in contact with the first object (afte…

In an experiment the following observations are made by a student for four charged objects W, X, Y, and Z:

• A glass rod rubbed with silk attracts W.
• W attracts Z but repels X.
• X attracts Z but repels Y.
• Y attracts W and Z.

Estimate whether the charges on each of the four objects are positive, negative, or neutral.

Common static electricity involves charges ranging from nanocoulombs to microcoulombs. (a) How many electrons are needed to form a charge of $–2.00 \text{nC}$ (b) How many electrons must be removed from a neutral object to leave a net charge of $0.500 \mu \text{C}$?

To start a car engine, the car battery moves $3 . \text{75} \times \text{10}^{\text{21}}$ electrons through the starter motor. How many coulombs of charge were moved?