Electrostatics

During a physics lab, a plastic strip was rubbed with cotton and became positively charged. The correct explanation for why the plastic strip becomes positively charged is that ...

• the plastic strip acquired extra protons from the cotton.
  
• the plastic strip acquired extra protons from the charging process 
• protons were created as the result of the charging process
  
• the plastic strip lost electrons to the cotton during the charging process 

A negatively charged plastic comb is brought close to, but does not touch, a small piece of paper. If the comb and the paper are attracted to each other, the charge on the paper

• must be positive
• must be negative
• may be neutral or negative
• may be neutral or positive 

Electrostatic force F exists between two point charges.

If the magnitude of both charges are doubled, the force between the charges will be...

• F
• 4F
• 2F
• F/4

The closer the charges, the ___________ the force between them

• closer
• further
• stronger
• weaker

Calculate the magnitude of force exerted between two charged objects separated by a distance of 0.6 m. One object has a charge of -5 C and the other has a charge of +2.0 C.

• 1.5x10¹¹ N

• 9.0x10¹⁰ N

• 2.5x10¹¹ N

• 7.5x10^-10 N

At which point is the electric field the weakest?

• A because it is the furthest away
• A because the field lines are further apart
• C because the field lines are further apart
• C  because it is the furthest away

What does it mean when the electric field lines are close together?

• the field is positive
• the field is negative
• The field is strong
• the field is weak

Based on the arrangement of the electric field lines in the diagram, what are the charges?

• both charges are the same

• the charges are opposite

• they are neutral; no charge

Consider the electric field lines shown in the diagram below. From the diagram, it is apparent that object A is ____ and object B is ____.

• +,+
• +,-
• -,+
• -,-

Is work done on the positive charge to move it from point A to point B?

• Yes

• No