PHYS 222 exam 1(Correctly solved)
.Suppose that a picture of electric field lines is drawn following the convention that 2 field lines
emerge from a small sphere with 2 pC of charge. In this picture there is an irregular closed
surface, the interior of which is hidden, as shown below. The net amount of charge inside the
closed surface must be: correct answers+4pc
Find the magnitude of the electric field produced by a point charge q = 3.96 AnanoCoulomb a
distance r = 3.6 meters from the charge in units of N/C. correct answersE=kQ/r^2
(8.99x10^9)x(3.96x10^-9)/(3.6)^2= 2.746
A certain physics textbook shows a region of space in which two electric field lines cross each
other. We should conclude that correct answersAuthor of text made a mistake
A cube with sides of area 24 cm2 contains a 48.1 nanoCoulomb charge. Find the flux of the
electric field through the surface of the cube in units of Nm2/C. correct answersE = Q/E0
(48.1 x 10^-9 C) / (8.85 x 10^-12 c^2/Nm^2) = 5435.028 Nm^2/C
Charges Q1 and Q2 are situated as shown below. The electric field is zero at point P. What
conclusions can be drawn about the charges Q1 and Q2? correct answersII. The magnitude of Q1
is greater than the magnitude of Q2.
IV. Q1 and Q2 have the same sign.
II and IV are correct
A positive charge is placed at one of 3 locations in a region where the electric field is uniform.
Compare the magnitude F of the electric force on the charge at the different locations. correct
answersF is the same, but not zero
In the early universe and in stars, deuterium nuclei are produced from the combination of one
proton and one neutron, with the release of a gamma ray. What is the charge on a deuterium
nucleus in units of qe = 1.6*10-19 C? correct answers1
Two uniformly charged spheres are firmly fastened to and electrically insulated from frictionless
pucks on an air table. The charge on sphere 2 is three times the charge on sphere 1. Which force
diagram correctly shows the magnitude and direction of the electrostatic forces? correct
answers5
Two balls rest on a frictionless surface. One ball is given a charge of +Q. The other ball is given
a charge of +3Q. Which diagram best represents the magnitude and direction of the force vectors
on the balls? correct answersC
Which of the following statements are true about the electric field? correct answers(b) The
strength of the electric field created by an object A at a point P decreases by a factor of 4 is the
distance between A and P is doubled
(d) The strength of the electric field inside a conductor is zero.
, (e) For irregularly shaped conductors, the electric field strength is greatest around points of
highest curvature.
(f) The SI unit for the electric field is N/C
Which of the following are true of static charges on everyday objects? correct answers(a) Like
charges repel.
(d) Opposite charges attract.
(e) A positively charged object has lost electrons.
(h) A negatively charged object has gained electrons.
A 93 microCoulomb charge is located at the origin and a -28 microCoulomb charge is located on
the y-axis at y = 44.8 cm. What is the magnitude of the force with which the charges attract each
other in units of N? correct answersF=(kq1q2)/r^2 k=9x10^9
F= [(9x10^9)(93x10^-6)(-28x10^-6)]/(0.448^2) = -116.768 = 116.77
When a positive charge is released from rest in a uniform electric field, it will correct
answersmove with constant acceleration.
Two positive point charges, each with charge q, separated by a distance d, repel each other with a
force of magnitude 10 N (a). What is the magnitude of the force between two positive point
charges of money
agnitude 6.57 q, separated by a distance 3.4 d in units of N (b)? correct answersF=kq^2/r^2
10N=kq2d2
xN=k6.57q23.4d2 (k is constant so it may be ignored)
xN=(6.5723.42)q2d2
xN=3.734q2d2`
The ratio in (a) of N:q2d2 is 10:1 so multiply 3.734*10 to get the new N.
37.34N=q2d2
Through rubbing an object has acquired a charge of -1 nanoCoulomb. correct answersElectron
transfer
Equipotential lines are shown. For which region is the magnitude of the electric field the
greatest? correct answersD
Which of the following statements are true about the electric potential or the electric potential
difference? correct answers(a) The SI unit of the electric potential is volts (V).
(f) The electric potential difference between two points is the difference in potential energy
possessed by another charge at those two points, divided by this charge.
Which of the following statements about a conductor in electrostatic equilibrium is false? correct
answersAnswer: All the above statements are true.
An electron travels through free space from point A, which is at 100 V, to point B, which is at
200 V. The kinetic energy of the electron during this trip.
delta KE = - delta PE = -(q*V) = -(-qe*V) = qe*V
.Suppose that a picture of electric field lines is drawn following the convention that 2 field lines
emerge from a small sphere with 2 pC of charge. In this picture there is an irregular closed
surface, the interior of which is hidden, as shown below. The net amount of charge inside the
closed surface must be: correct answers+4pc
Find the magnitude of the electric field produced by a point charge q = 3.96 AnanoCoulomb a
distance r = 3.6 meters from the charge in units of N/C. correct answersE=kQ/r^2
(8.99x10^9)x(3.96x10^-9)/(3.6)^2= 2.746
A certain physics textbook shows a region of space in which two electric field lines cross each
other. We should conclude that correct answersAuthor of text made a mistake
A cube with sides of area 24 cm2 contains a 48.1 nanoCoulomb charge. Find the flux of the
electric field through the surface of the cube in units of Nm2/C. correct answersE = Q/E0
(48.1 x 10^-9 C) / (8.85 x 10^-12 c^2/Nm^2) = 5435.028 Nm^2/C
Charges Q1 and Q2 are situated as shown below. The electric field is zero at point P. What
conclusions can be drawn about the charges Q1 and Q2? correct answersII. The magnitude of Q1
is greater than the magnitude of Q2.
IV. Q1 and Q2 have the same sign.
II and IV are correct
A positive charge is placed at one of 3 locations in a region where the electric field is uniform.
Compare the magnitude F of the electric force on the charge at the different locations. correct
answersF is the same, but not zero
In the early universe and in stars, deuterium nuclei are produced from the combination of one
proton and one neutron, with the release of a gamma ray. What is the charge on a deuterium
nucleus in units of qe = 1.6*10-19 C? correct answers1
Two uniformly charged spheres are firmly fastened to and electrically insulated from frictionless
pucks on an air table. The charge on sphere 2 is three times the charge on sphere 1. Which force
diagram correctly shows the magnitude and direction of the electrostatic forces? correct
answers5
Two balls rest on a frictionless surface. One ball is given a charge of +Q. The other ball is given
a charge of +3Q. Which diagram best represents the magnitude and direction of the force vectors
on the balls? correct answersC
Which of the following statements are true about the electric field? correct answers(b) The
strength of the electric field created by an object A at a point P decreases by a factor of 4 is the
distance between A and P is doubled
(d) The strength of the electric field inside a conductor is zero.
, (e) For irregularly shaped conductors, the electric field strength is greatest around points of
highest curvature.
(f) The SI unit for the electric field is N/C
Which of the following are true of static charges on everyday objects? correct answers(a) Like
charges repel.
(d) Opposite charges attract.
(e) A positively charged object has lost electrons.
(h) A negatively charged object has gained electrons.
A 93 microCoulomb charge is located at the origin and a -28 microCoulomb charge is located on
the y-axis at y = 44.8 cm. What is the magnitude of the force with which the charges attract each
other in units of N? correct answersF=(kq1q2)/r^2 k=9x10^9
F= [(9x10^9)(93x10^-6)(-28x10^-6)]/(0.448^2) = -116.768 = 116.77
When a positive charge is released from rest in a uniform electric field, it will correct
answersmove with constant acceleration.
Two positive point charges, each with charge q, separated by a distance d, repel each other with a
force of magnitude 10 N (a). What is the magnitude of the force between two positive point
charges of money
agnitude 6.57 q, separated by a distance 3.4 d in units of N (b)? correct answersF=kq^2/r^2
10N=kq2d2
xN=k6.57q23.4d2 (k is constant so it may be ignored)
xN=(6.5723.42)q2d2
xN=3.734q2d2`
The ratio in (a) of N:q2d2 is 10:1 so multiply 3.734*10 to get the new N.
37.34N=q2d2
Through rubbing an object has acquired a charge of -1 nanoCoulomb. correct answersElectron
transfer
Equipotential lines are shown. For which region is the magnitude of the electric field the
greatest? correct answersD
Which of the following statements are true about the electric potential or the electric potential
difference? correct answers(a) The SI unit of the electric potential is volts (V).
(f) The electric potential difference between two points is the difference in potential energy
possessed by another charge at those two points, divided by this charge.
Which of the following statements about a conductor in electrostatic equilibrium is false? correct
answersAnswer: All the above statements are true.
An electron travels through free space from point A, which is at 100 V, to point B, which is at
200 V. The kinetic energy of the electron during this trip.
delta KE = - delta PE = -(q*V) = -(-qe*V) = qe*V
