Phys 2002 Midterm Practice Questions And Detailed Solutions

PHYS 2002 MIDTERM PRACTICE QUESTIONS
AND DETAILED SOLUTIONS

◉ Complete the following statement: When an ebonite rod is rubbed
with animal fur, the rod becomes negatively charged as
A)positive charges are transferred from the fur to the rod
B)negative charges are transferred from the rod to the fur
C) negative charges are created on the surface of the rod
D) negative charges are transferred from the fur to the rod
E)positive charges are transferred from the rod the fur.
Answer: D) negative charges are transferred from the fur to the rod


◉ Complete the following statement: When a glass rod is rubbed
with silk cloth, the rod becomes positively charged as
A)positive charges are transferred from the silk to the rod
B)negative charges are transferred from the rod to the silk
C)positive charges are created on the surface of the rod
D)negative charges are transferred from silk to the rod
E)positive charges are transferred from the rod to the silk.
Answer: B)negative charges are transferred from the rod to the silk

,◉ A charged conductor is brought near an uncharged insulator.
Which one of the following statements is true?
A)both objects will repel each other
B)both objects will attract each other
C)neither object exerts an electrical force on the other
D)the objects will repel each other only if the conductor has a
negative charge
E)the objects will repel each other only if the conductor has a
positive charge.
Answer: B)both objects will attract each other


◉ Two charged particles A and B are located near one another. Both
the magnitude and direction of the force particle A exerts on particle
B is independent of
A)the sign of charge B
B)the sign of charge A
C)the distance between A and B
D)the magnitude of the charge on B
E) the magnitude and direction of the force are dependent on all of
the above choices.
Answer: E) the magnitude and direction of the force are dependent
on all of the above choices

,◉ Two positive point charges Q and 2Q are separated by a distance
R. If the charge Q experiences a force of magnitude F when the
separation is R, what is the magnitude of the force on the charge 2Q
when the separation is 2R?
A)F/4
B)F/2
C)F
D)2F
E)4F.
Answer: E)4F


◉ In Frame 1, two identical conducting spheres, A and B, carry equal
amounts of excess charge that have the same sign. The spheres are
separated by a distance d; and sphere A exerts an electrostatic force
on sphere B that has a magnitude F. A third sphere, C, which is
handled only by an insulating rod, is introduced in Frame 2. Sphere C
is identical to A and B except that it is initially uncharged. Sphere C is
touched first to sphere A, in Frame 2, and then to sphere B, in Frame
3, and is finally removed in Frame 4.
Determine the magnitude of the electrostatic force that sphere A
exerts on sphere B in Frame 4.
A) F/2
B) F/3
C) 3F/4
D) 3F/8

, E) zero.
Answer: D) 3F/8


◉ The figure shows an equilateral triangle ABC. A positive point
charge +q is located at each of the three vertices A, B, and C. Each
side of the triangle is of length a. A point charge Q (that may be
positive or negative) is placed at the mid-point between B and C.
Is it possible to choose the value of Q (that is non-zero) such that
the force on Q is zero? Explain why or why not.
A) Yes, because the forces on Q are vectors and three vectors can add
to zero.
B) No, because the forces on Q are vectors and three vectors can
never add to zero.
C) Yes, because the electric force at the mid-point between B and C is
zero whether a charge is placed there or not.
D) No, because the forces on Q due to the charges at B and C point in
the same direction.
E) No, because a fourth charge would be needed to cancel the force
on Q due to the charge at A..
Answer: E) No, because a fourth charge would be needed to cancel
the force on Q due to the charge at A.


◉ In the figure, point A is a distance L away from a point charge Q.
Point B is a distance 4L away from Q. What is the ratio of the electric
field at B to that at A, EB/EA?