Physics Take Home Test Chapter 16
Due May 7, 2015 at 8 am
Mrs. Ashley
Name __________Key_________________________
____c____1. Which
force binds atoms together to form molecules?
A) gravitational
B) nuclear
C) electrical
D) centripetal
E) none of these
____c___ 2. A
positive ion has more
A) electrons than neutrons.
B) electrons than protons.
C) protons than electrons.
D) protons than neutrons.
E) neutrons than protons.
___b_____ 3.
A main difference between gravitational and electric forces is that electrical forces
A) attract.
B) repel or attract.
C) obey the inverse-square law.
D) act over shorter distances.
E) are weaker
___c____ 4. The electrical force between charges depends only on the charges'
A) magnitude.
B) separation distance.
C) magnitude and separation distance.
D) None of the above choices are correct.
___a_____ 5. When
the distance between two charges is halved, the electrical force between the
charges
A) quadruples.
B) doubles.
C) halves.
D) is reduced by 1/4.
E) None of the above choices are correct.
A difference between electric forces and gravitational forces is that gravitational
forces are not affected by
A) separation distance.
B) repulsive interaction.
C) the inverse-square law.
D) infinite range.
E) None of the above choices are correct.
___b____ 6.
__d_____ 7. The symbol 0 represents
A) electric field
B) dielectric constant
C) on coulomb
D) permittivity of free space
E) none of the above
____a___8. A material that allows a charge to move easily within them is called
A) a conductor
B) an insulator
C) a polarized object
D) an electric field
E) none of the above
____e___ 9. A conductor differs from an insulator in that a conductor
A) has more electrons than protons.
B) has more protons than electrons.
C) has more energy than an insulator.
D) has faster moving molecules.
E) none of these
____d___ 10. The direction of an electric field is the direction of the force that the field would
exert on
A) a neutral test charge.
B) an electron.
C) an atom.
D) a proton.
E) a molecule.
____c___ 11. Two charges separated by one meter exert 1-N forces on each other. If the
magnitude of each charge is doubled, the force on each charge is
A) 1 N.
B) 2 N.
C) 4 N.
D) 8 N.
E) None of the above choices are correct.
__b_____ 12. The electric field inside an uncharged metal ball is zero. If the ball is negatively
charged, the electric field inside the ball is then
A) less than zero.
B) zero.
C) greater than zero.
_____A__ 13. Two electrons are passing 26.0 mm apart. What is the electric repulsive force that
they exert on each other? (The value of k is 9.0 × 109 N · m2/C2.)
A) 3.4 × 10-25 N
B) 1.3 × 1010 N
C) 1.3 N
D) 3.4 × 10-27 N
___B____14. If you rub a balloon on your sweater and then press it to a wall, it will often stick
there. Why does this happen?
A) Rubbing removes a surface layer of grease, allowing the rubber to come in sufficiently close
contact with the wall so that air pressure holds it there.
B) Rubbing the balloon charges it electrostatically, and this charge on the balloon induces an
opposite charge on the wall. The attraction between the induced charge and the charge on the
balloon holds the balloon to the wall.
C) A wall typically has a net electric charge on it, and rubbing the balloon charges it
electrostatically. If the wall happens to have opposite charge to that on the balloon, the balloon
will stick.
D) Rubbing the balloon causes moisture to condense on it, and surface tension causes the balloon
to stick to the wall.
E) Rubbing the balloon surface causes it to become slightly conducting. When the balloon is
touched to the wall, electrons flow from the balloon to the wall. This sets up an electric field that
bonds the balloon weakly to the wall.
Problems- Please show include the free body diagram, the formula used, substitute the values for
the formula and solve for complete credit.
15.- 18 (worth 4 points) A charge q = +3.0 nC is placed at a location at which the electri field
strength is 400N/C. Find the force felt by the charge q.
F= qE
1.2 x 10-6 N
19-22 (Worth 4 points). Consider two small spheres, one carrying a charge of +1.5 nC and the other a
charge of -2.0 nC separated by a distance of 1.5 cm. Find the electric force between them. (n is the
abbreviation for "nano" which means 10-9)
-1.2 x10-6 N
23-26. (four points)Two point charges have a total charge of 560C. When placed 1.4 m apart, the
force each exerts on the other is 20.4 N and is repulsive. What is the charge on each?
q = -5.52 X 10-4 C
Q-q = -8.31 X 10-6 C
q = -8.05 X 10-6 C
Q-q = 5.52 X 10-4 C
27-30. (four points). Charges of +4.20 C are placed at the opposite corners of a square and -4.20 C
are placed at the other opposite corners of the square that has a length of 1.50 m on a side. Determine
the magnitude and direction of the force on one of the positive charges.
2.96 X 107 N
225 degrees from the x axis towards the center.