Model Answer for Q1

PHYS 131
29 Jan 2016
College of Engineering
Quiz No. 2
- Charges of the same sign repel one another and charges with opposite signs
attract one another.
(2 marks)
- When we write q = ±Ne, where N is some integer for describing one of the
charge properties ,this property is quantization
(2 marks)
Three objects are brought close to one another, two at a time. When objects
A and B are brought together, they attract. When objects B and C are
brought together, they repel. Which of the following are necessarily true?
(a) Objects A and C possess charges of the same sign.
(b) Objects A and C possess charges of opposite sign.
(c) All three objects possess charges of the same sign.
(d) One object is neutral.
(e) Additional experiments must be performed to determine information
about the charges on the objects.
(5 marks)
(b), (e). The experiment shows that A and B have charges of the
opposite sign but objects B and C have the same sign.. We cannot
determine from this information, however, if the charges are
positive or negative.
Two point charges separated by a distance r exert a force on each other
that is given by Coulomb’s law. The force F21 exerted by q2 on q1 is equal in
magnitude and opposite in direction to the force F12 exerted by q1 on
(1 mark)
Best of Luck
Prof. Dr. GAMAL