Snead State PHY Final
You are given two metal spheres on portable insulating stands, a glass rod, and a piece
of silk. Explain how to give the spheres exactly equal but opposite charges. -
CORRECT ANSWER-By rubbing the the glass rod with the silk cloth, the glass rod gets
a positive charge and the silk cloth gets equal and opposite charge that is negative.
A metal rod A and a metal sphere B, on insulating stands, touch each other as shown in
Figure Q20.9. They are originally neutral. A positively charged rod is brought near (but
not touching) the far end of A. While the charged rod is still close, A and B are
separated. The charged rod is then withdrawn. Is the sphere then positively charged,
negatively charged, or neutral? Explain. - CORRECT ANSWER-sphere is then
positively charged
A positively charged particle is in the center of a parallel - plate capacitor that has
charge +- Q on its plates. Suppose the distance between the plates is doubled, with the
charged particle remaining in the center. Does the force on this particle increase,
decrease, or stay the same? Explain. - CORRECT ANSWER-stay the same!
A glass rod that has been charged to +12 nC touches a metal sphere. Afterward, the
rod's charge is +8.0 nC.
a.) What kind of charged particle was transferred between the rod and the sphere, and
in which direction? That is, did it move from the rod to the sphere or from the sphere to
the rod?
b.) How many charged particles were transferred? - CORRECT ANSWER-a.) electrons
have moved from sphere toward rod
b.) 2.5 x 10^10 electrons
A small plastic sphere with a charge of -5.0 nC is near another small plastic sphere with
a charge of -12nC. If the spheres repel one another with a force of magnitude 8.2 x 10^-
4 N, what is the distance between the spheres? - CORRECT ANSWER-0.026 m or 2.57
cm
What are the strength and direction of the electric field 2.0 cm from a small glass bead
that has been charged to +6.0 nC? - CORRECT ANSWER-1.4 x 10^5 N/C away from
the bead
As shown in Figure Q21.6, two protons are launched with the same speed from point 1
inside a parallel-plate capacitor. One proton moves along the path from 1 to 2, the other
from 1 to 3. Points 2 and 3 are the same distance from the positive plate.
, a.) Is delta U 1-->2, the change in potential energy along the path 1 --> 2 larger than,
smaller than, or equal to delta U 1 --> 3? Explain
b.)the proton's speed v2 at point 2 larger than, smaller than, or equal to the proton's
speed v3 at point 3? Explain. - CORRECT ANSWER-a.) They would be equal to each
other
b.) V2 = V3
Each part of Figure Q21.7 shows one or more point charges. The charges have equal
magnitudes. If a positive charge is moved from position i to position f, does the electric
potential energy increase, decrease, or stay the same? Explain. - CORRECT
ANSWER-
Rank in order, from largest to smallest, the electric field strengths E1, E2, E3, and E4 at
the four labeled points in Figure Q21.13. Explain. - CORRECT ANSWER-
Figure Q21.14 shows an electric field diagram. Rank in order, from highest to lowest,
the electric potentials at points a, b, and c. - CORRECT ANSWER-
Moving a charge from point A, where the potential is 300 V, to point B, where the
Moving a charge from point A, where the potential is 300 V, to point B, where the
potential is 150 V, takes 4.5 x 10^-4 J of work. What is the value of the charge? -
CORRECT ANSWER--3uC
This scanning electron microscope image of a bacterium was produced using a beam of
electrons accelerated through an 30 kV potential difference. What is the speed of the
electrons? - CORRECT ANSWER-1.026 x 10^8 m/sec
Under typical atmospheric conditions, there is an electric field near the earth's surface,
directed downward, with a magnitude of 100 V/m. If we say that the potential at the
earth's surface is 0 V, what is the potential 1.0 km above the surface? - CORRECT
ANSWER-
A switch that connects a battery to a 10uF capacitor is closed. Several seconds later
you find that the capacitor plates are charged to +- 30 uC. What is the battery voltage? -
CORRECT ANSWER-3 volts
To what potential should you charge a 1 uF capacitor to store 1.0 J of energy? -
CORRECT ANSWER-1.41 kV
Cells in the nervous system have a potential difference of 70 mV across the cell
membrane separating the interior of the cell from the extracellular fluid. This potential
You are given two metal spheres on portable insulating stands, a glass rod, and a piece
of silk. Explain how to give the spheres exactly equal but opposite charges. -
CORRECT ANSWER-By rubbing the the glass rod with the silk cloth, the glass rod gets
a positive charge and the silk cloth gets equal and opposite charge that is negative.
A metal rod A and a metal sphere B, on insulating stands, touch each other as shown in
Figure Q20.9. They are originally neutral. A positively charged rod is brought near (but
not touching) the far end of A. While the charged rod is still close, A and B are
separated. The charged rod is then withdrawn. Is the sphere then positively charged,
negatively charged, or neutral? Explain. - CORRECT ANSWER-sphere is then
positively charged
A positively charged particle is in the center of a parallel - plate capacitor that has
charge +- Q on its plates. Suppose the distance between the plates is doubled, with the
charged particle remaining in the center. Does the force on this particle increase,
decrease, or stay the same? Explain. - CORRECT ANSWER-stay the same!
A glass rod that has been charged to +12 nC touches a metal sphere. Afterward, the
rod's charge is +8.0 nC.
a.) What kind of charged particle was transferred between the rod and the sphere, and
in which direction? That is, did it move from the rod to the sphere or from the sphere to
the rod?
b.) How many charged particles were transferred? - CORRECT ANSWER-a.) electrons
have moved from sphere toward rod
b.) 2.5 x 10^10 electrons
A small plastic sphere with a charge of -5.0 nC is near another small plastic sphere with
a charge of -12nC. If the spheres repel one another with a force of magnitude 8.2 x 10^-
4 N, what is the distance between the spheres? - CORRECT ANSWER-0.026 m or 2.57
cm
What are the strength and direction of the electric field 2.0 cm from a small glass bead
that has been charged to +6.0 nC? - CORRECT ANSWER-1.4 x 10^5 N/C away from
the bead
As shown in Figure Q21.6, two protons are launched with the same speed from point 1
inside a parallel-plate capacitor. One proton moves along the path from 1 to 2, the other
from 1 to 3. Points 2 and 3 are the same distance from the positive plate.
, a.) Is delta U 1-->2, the change in potential energy along the path 1 --> 2 larger than,
smaller than, or equal to delta U 1 --> 3? Explain
b.)the proton's speed v2 at point 2 larger than, smaller than, or equal to the proton's
speed v3 at point 3? Explain. - CORRECT ANSWER-a.) They would be equal to each
other
b.) V2 = V3
Each part of Figure Q21.7 shows one or more point charges. The charges have equal
magnitudes. If a positive charge is moved from position i to position f, does the electric
potential energy increase, decrease, or stay the same? Explain. - CORRECT
ANSWER-
Rank in order, from largest to smallest, the electric field strengths E1, E2, E3, and E4 at
the four labeled points in Figure Q21.13. Explain. - CORRECT ANSWER-
Figure Q21.14 shows an electric field diagram. Rank in order, from highest to lowest,
the electric potentials at points a, b, and c. - CORRECT ANSWER-
Moving a charge from point A, where the potential is 300 V, to point B, where the
Moving a charge from point A, where the potential is 300 V, to point B, where the
potential is 150 V, takes 4.5 x 10^-4 J of work. What is the value of the charge? -
CORRECT ANSWER--3uC
This scanning electron microscope image of a bacterium was produced using a beam of
electrons accelerated through an 30 kV potential difference. What is the speed of the
electrons? - CORRECT ANSWER-1.026 x 10^8 m/sec
Under typical atmospheric conditions, there is an electric field near the earth's surface,
directed downward, with a magnitude of 100 V/m. If we say that the potential at the
earth's surface is 0 V, what is the potential 1.0 km above the surface? - CORRECT
ANSWER-
A switch that connects a battery to a 10uF capacitor is closed. Several seconds later
you find that the capacitor plates are charged to +- 30 uC. What is the battery voltage? -
CORRECT ANSWER-3 volts
To what potential should you charge a 1 uF capacitor to store 1.0 J of energy? -
CORRECT ANSWER-1.41 kV
Cells in the nervous system have a potential difference of 70 mV across the cell
membrane separating the interior of the cell from the extracellular fluid. This potential
