PHY 112 EXAM 1 REVIEW QUESTIONS AND ANSWERS
1. An object carries a charge of -6.1 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?: 1.28E14
2. 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 12
electrons? Be sure to include the algebraic sign (+ or -) in your
answer.: +2.24E-18 C
3. 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 2.31 liters of water? (1 liter is equivalent to 1.00 × 10-3 m3) (b)
What is the net charge of all these electrons?: (a)
773000000000000000000000000
(b) -123651733.3 C
4. An electrically isolated object is electrically neutral. What is the
charge on the object if you remove three electrons?
(a)Zero
(b)-3e
(c) +3e
(d) Impossible to tell: +3e
5. The nucleus of the nitrogen atom has 7 protons. How many
electrons does an electrical neutral nitrogen atom have?
(a)0
(b) 3
,(c)Impossible to tell
(d)7: 7
,6. An electrically neutral balloon is rubbed on cloth and becomes
positively charged. What can be said about its mass?
The mass decreases.
The mass increases.
It does not change.: The mass decreases
7. 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?
It has no effect on the trajectory of the
electron. It deflects the electron to the
right.
It deflects the electron to the left.
Impossible to tell: It deflects the electron to the right
8. 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?
The force increases by a factor
of 2. The force increases by a
factor of 4. The force increases
by a factor of 16.
The force increases by a factor of 8.: The force increases by a factor of 16
, 9. What is the electrostatic force between and electron and a
proton separated by 0.1 mm?
2.3 × 10-20 N, attractive.
1. An object carries a charge of -6.1 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?: 1.28E14
2. 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 12
electrons? Be sure to include the algebraic sign (+ or -) in your
answer.: +2.24E-18 C
3. 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 2.31 liters of water? (1 liter is equivalent to 1.00 × 10-3 m3) (b)
What is the net charge of all these electrons?: (a)
773000000000000000000000000
(b) -123651733.3 C
4. An electrically isolated object is electrically neutral. What is the
charge on the object if you remove three electrons?
(a)Zero
(b)-3e
(c) +3e
(d) Impossible to tell: +3e
5. The nucleus of the nitrogen atom has 7 protons. How many
electrons does an electrical neutral nitrogen atom have?
(a)0
(b) 3
,(c)Impossible to tell
(d)7: 7
,6. An electrically neutral balloon is rubbed on cloth and becomes
positively charged. What can be said about its mass?
The mass decreases.
The mass increases.
It does not change.: The mass decreases
7. 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?
It has no effect on the trajectory of the
electron. It deflects the electron to the
right.
It deflects the electron to the left.
Impossible to tell: It deflects the electron to the right
8. 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?
The force increases by a factor
of 2. The force increases by a
factor of 4. The force increases
by a factor of 16.
The force increases by a factor of 8.: The force increases by a factor of 16
, 9. What is the electrostatic force between and electron and a
proton separated by 0.1 mm?
2.3 × 10-20 N, attractive.
