An object carries a charge of -7.2 µC, while another carries a charge of -2.0 µC.
How many electrons must be transferred from the first to the second object so
that both objects have the same charge?
Number of electrons = Number - ANSWER 1.625E13 no units
Iron atoms have been detected in the sun's atmosphere, some with many of their
electrons stripped away. What is the net electric charge (in coulombs) of an iron
atom with 26 protons and 11 electrons? Be sure to include the algebraic sign (+ or
-) in your answer. - ANSWER +2.4E-18 C
Water has a mass per mole of 18.0 g/mol, and each water molecule (H2O) has 10
electrons. (a) How many electrons are there in 2.79 liters of water? (1 liter is
equivalent to 1.00 × 10-3 m3) (b) What is the net charge of all these electrons? -
ANSWER a). 9.331E26 no units b.) -1.493 E8 C
In a vacuum, two particles have charges of q1 and q2, where q1 = +4.4C. They are
separated by a distance of 0.22 m, and particle 1 experiences an attractive force
of 3.9 N. What is the value of q2, with its sign? - ANSWER -4.76E-6 C
An electric field of 480000 N/C points due west at a certain spot. What is the
magnitude of the force that acts on a charge of -7.5C at this spot? - ANSWER 3.6
N
A tiny ball (mass = 0.011 kg) carries a charge of -21C. What is the electric field
magnitude that would cause the ball to float above the ground? - ANSWER
5138.09 N/C
Charge q1 is placed a distance r0 from charge q2. What happens to the
magnitude of the force on q1 due to q2 if the distance between them is reduced to
r0/4? - ANSWER the force increases by factor of 16
What is the electrostatic force between and electron and a proton separated by
0.1 mm? - ANSWER 2.3E-20 N attractive
PHY 112 FINAL EXAM WITH 100% CORRECT ANSWERS!
,Three point charges have equal magnitudes and are located on the same line. The
separation d between A and B is the same as that between B and C. One of the
charges is positive and two are negative, as the drawing shows. Consider the net
electrostatic force that each charge experiences due to the other two charges.
Rank the net forces in descending order (greatest first) according to magnitude. -
ANSWER B,A,C
Because of an electric field, a positive charge +q experiences a force of
magnitude F that points due west. The positive charge is then replaced with a
negative charge -2q. What force does the negative charge experience? - ANSWER
force magnitude =2F, force direction is due east
The drawing shows a positive and a negative point charge. The negative charge
has the greater magnitude. Where on the line that passes through the charges is
the one spot where the total electric field is zero? - ANSWER to the left of the
positive charge
Two charges attract each other with a force of 8.9 N. What will be the force if the
distance between them is reduced to one-ninth of its original value? - ANSWER
720.9 N
An electrically isolated object is electrically neutral. What is the charge on the
object if you remove three electrons? - ANSWER +3e
The nucleus of the nitrogen atom has 7 protons. How many electrons does an
electrical neutral nitrogen atom have? - ANSWER 7
An electrically neutral balloon is rubbed on cloth and becomes positively
charged. What can be said about its mass? - ANSWER the mass decreases
Suppose an electron is moving with a constant velocity until it encounters a
positively charged sphere on its right. How does the sphere alter the trajectory of
the electron? - ANSWER it defects the electron to the right
Which one of the following is a good conductor? - ANSWER lead
If you place a large number of electrons in one small spot on a conductor, they
immediately redistribute themselves on the surface because they repel one
another. What happens if you place a large number of electron in one small are on
the surface of an insulator? - ANSWER They stay in the area in which they were
initially deposited for a relatively long time because they are not free to move
about the insulator.
PHY 112 FINAL EXAM WITH 100% CORRECT ANSWERS!
, Suppose a thin conducting wire connects two conducting spheres. A negatively
charged rod is brought near one of the spheres, the wire between them is cut,
and the charged rod is taken away. Which one of the following is true? - ANSWER
The spheres will attract each other
When you bring a negatively charged rod near a piece of electrically neutral
plastic it attracts it. What happens if you instead bring a positively charged rod
near the plastic? - ANSWER it attracts
Suppose a negative point charge is placed at x=0 and an electron is placed at
some point P on the positive x-axis. What is the direction of the electric field at
point P due to the point charge, and what is the direction of the force experienced
by the electron due to that field? - ANSWER along -x; F along +x
What is magnitude of the acceleration of a particle of mass m and charge +Q
placed between the plates of a parallel plate capacitor of charge density σ? -
ANSWER a=Qo/Eom
The membrane surrounding a living cell consists of an inner and an outer wall
that are separated by a small space. Assume that the membrane acts like a
parallel plate capacitor in which the effective charge density on the inner and
outer walls has a magnitude of 7.3 × 10-6 C/m2. (a) What is the magnitude of the
electric field within the cell membrane? (b) Find the magnitude of the electric
force that would be exerted on a potassium ion (K+; charge = +e) placed inside
the membrane. - ANSWER a. 8.24E5 N/C b. 1.3E-13 N
Suppose a charge -6q is suspended inside a cavity in an electrically neutral
cylindrical conductor. What is the charge induced on the interior surface? -
ANSWER +6q
Suppose a charge -6q is suspended inside a cavity in an electrically neutral
cylindrical conductor. What is the charge induced on the exterior surface? -
ANSWER -6q
A collection of 11 electrons and 4 protons are contained in a Gaussian (i.e.,
closed) surface. What is the total electric flux through the surface? - ANSWER
7e/eo
An electric field is constant at every point on a square surface that is 0.80 m on a
side. This field has a magnitude of 3.6 N/C and is oriented at an angle of 35° with
PHY 112 FINAL EXAM WITH 100% CORRECT ANSWERS!
How many electrons must be transferred from the first to the second object so
that both objects have the same charge?
Number of electrons = Number - ANSWER 1.625E13 no units
Iron atoms have been detected in the sun's atmosphere, some with many of their
electrons stripped away. What is the net electric charge (in coulombs) of an iron
atom with 26 protons and 11 electrons? Be sure to include the algebraic sign (+ or
-) in your answer. - ANSWER +2.4E-18 C
Water has a mass per mole of 18.0 g/mol, and each water molecule (H2O) has 10
electrons. (a) How many electrons are there in 2.79 liters of water? (1 liter is
equivalent to 1.00 × 10-3 m3) (b) What is the net charge of all these electrons? -
ANSWER a). 9.331E26 no units b.) -1.493 E8 C
In a vacuum, two particles have charges of q1 and q2, where q1 = +4.4C. They are
separated by a distance of 0.22 m, and particle 1 experiences an attractive force
of 3.9 N. What is the value of q2, with its sign? - ANSWER -4.76E-6 C
An electric field of 480000 N/C points due west at a certain spot. What is the
magnitude of the force that acts on a charge of -7.5C at this spot? - ANSWER 3.6
N
A tiny ball (mass = 0.011 kg) carries a charge of -21C. What is the electric field
magnitude that would cause the ball to float above the ground? - ANSWER
5138.09 N/C
Charge q1 is placed a distance r0 from charge q2. What happens to the
magnitude of the force on q1 due to q2 if the distance between them is reduced to
r0/4? - ANSWER the force increases by factor of 16
What is the electrostatic force between and electron and a proton separated by
0.1 mm? - ANSWER 2.3E-20 N attractive
PHY 112 FINAL EXAM WITH 100% CORRECT ANSWERS!
,Three point charges have equal magnitudes and are located on the same line. The
separation d between A and B is the same as that between B and C. One of the
charges is positive and two are negative, as the drawing shows. Consider the net
electrostatic force that each charge experiences due to the other two charges.
Rank the net forces in descending order (greatest first) according to magnitude. -
ANSWER B,A,C
Because of an electric field, a positive charge +q experiences a force of
magnitude F that points due west. The positive charge is then replaced with a
negative charge -2q. What force does the negative charge experience? - ANSWER
force magnitude =2F, force direction is due east
The drawing shows a positive and a negative point charge. The negative charge
has the greater magnitude. Where on the line that passes through the charges is
the one spot where the total electric field is zero? - ANSWER to the left of the
positive charge
Two charges attract each other with a force of 8.9 N. What will be the force if the
distance between them is reduced to one-ninth of its original value? - ANSWER
720.9 N
An electrically isolated object is electrically neutral. What is the charge on the
object if you remove three electrons? - ANSWER +3e
The nucleus of the nitrogen atom has 7 protons. How many electrons does an
electrical neutral nitrogen atom have? - ANSWER 7
An electrically neutral balloon is rubbed on cloth and becomes positively
charged. What can be said about its mass? - ANSWER the mass decreases
Suppose an electron is moving with a constant velocity until it encounters a
positively charged sphere on its right. How does the sphere alter the trajectory of
the electron? - ANSWER it defects the electron to the right
Which one of the following is a good conductor? - ANSWER lead
If you place a large number of electrons in one small spot on a conductor, they
immediately redistribute themselves on the surface because they repel one
another. What happens if you place a large number of electron in one small are on
the surface of an insulator? - ANSWER They stay in the area in which they were
initially deposited for a relatively long time because they are not free to move
about the insulator.
PHY 112 FINAL EXAM WITH 100% CORRECT ANSWERS!
, Suppose a thin conducting wire connects two conducting spheres. A negatively
charged rod is brought near one of the spheres, the wire between them is cut,
and the charged rod is taken away. Which one of the following is true? - ANSWER
The spheres will attract each other
When you bring a negatively charged rod near a piece of electrically neutral
plastic it attracts it. What happens if you instead bring a positively charged rod
near the plastic? - ANSWER it attracts
Suppose a negative point charge is placed at x=0 and an electron is placed at
some point P on the positive x-axis. What is the direction of the electric field at
point P due to the point charge, and what is the direction of the force experienced
by the electron due to that field? - ANSWER along -x; F along +x
What is magnitude of the acceleration of a particle of mass m and charge +Q
placed between the plates of a parallel plate capacitor of charge density σ? -
ANSWER a=Qo/Eom
The membrane surrounding a living cell consists of an inner and an outer wall
that are separated by a small space. Assume that the membrane acts like a
parallel plate capacitor in which the effective charge density on the inner and
outer walls has a magnitude of 7.3 × 10-6 C/m2. (a) What is the magnitude of the
electric field within the cell membrane? (b) Find the magnitude of the electric
force that would be exerted on a potassium ion (K+; charge = +e) placed inside
the membrane. - ANSWER a. 8.24E5 N/C b. 1.3E-13 N
Suppose a charge -6q is suspended inside a cavity in an electrically neutral
cylindrical conductor. What is the charge induced on the interior surface? -
ANSWER +6q
Suppose a charge -6q is suspended inside a cavity in an electrically neutral
cylindrical conductor. What is the charge induced on the exterior surface? -
ANSWER -6q
A collection of 11 electrons and 4 protons are contained in a Gaussian (i.e.,
closed) surface. What is the total electric flux through the surface? - ANSWER
7e/eo
An electric field is constant at every point on a square surface that is 0.80 m on a
side. This field has a magnitude of 3.6 N/C and is oriented at an angle of 35° with
PHY 112 FINAL EXAM WITH 100% CORRECT ANSWERS!
