PHY 242 Exam 2 UPDATED ACTUAL
QUESTIONS AND CORRECT ANSWERS
The voltage across each capacitor in a set of capacitors in series is... - CORRECT
ANSWER inversely proportional to its capacitance
A capacitor is connected to a battery. When a dielectric is inserted between the plates of the
capacitor... - CORRECT ANSWER both the capacitance and the charge change
The electric potential inside a capacitor... - CORRECT ANSWER increases linearly from the
negative to the positive plate.
Two identical capacitors A and B are connected in parallel with each other across a battery. If mica (of
dielectric constant 5.4) is inserted in B: - CORRECT ANSWER B will have the larger charge
A parallel plate capacitor is connected to a battery and charged to voltage V. Leah says that the charge
on the plates will decrease if the distance between the plates is increased while they are still connected
to the battery. Gertie says that the charge will remain the same. Which one, if either, is correct, and
why? - CORRECT ANSWER Leah, because the capacitance decreases when the plate
separation is increased.
If the area of the plates of a parallel plate capacitor is doubled, the capacitance is... - CORRECT
ANSWER doubled
Consider a pair of two identical capacitors. In which case is the capacitance of the pair greater? -
CORRECT ANSWER When they are connected in parallel with each other.
In a loop in a closed circuit, the sum of the currents entering a junction equals the sum of the currents
leaving a junction because... - CORRECT ANSWER charge is neither created nor destroyed at
a junction.
The algebraic sum of the changes of potential around any closed circuit loop is... - CORRECT
ANSWER zero
, The battery is disconnected from a series RC circuit after the capacitor is fully charged and is replaced
by an open switch. When the switch is closed... - CORRECT ANSWER the capacitor does not
allow current to pass.
Consider a capacitor which is charged to 12 volts and then connected across a resistor. Let t1/2 be the
time it takes for the voltage to drop down to 6 volts. Suppose the experiment is repeated, but with a
pair of capacitors connected in parallel with each other in place of the original capacitor, where each
element of the pair has the same capacitance as the original capacitor. How does the new t1/2 compare
with the original t1/2? - CORRECT ANSWER The new t1/2 is twice the original t1/2.
A junior Thomas Edison wants to make a brighter light bulb. He decides to modify the filament. How
should the filament of a light bulb be modified in order to make the light bulb produce more light at a
given voltage? - CORRECT ANSWER increase the diameter only
An electron moving in the positive x direction experiences a magnetic force in the positive z direction.
If Bx = 0, what is the direction of the magnetic field? - CORRECT ANSWER negative y
direction
A positively-charged particle is moving southward in a downward-directed uniform magnetic field.
The magnetic force is the only force, if any, acting on the particle. During the next few centimeters of
its travel... - CORRECT ANSWER the particle keeps on going at the same speed.
A positively-charged particle is moving southward in a downward-directed uniform magnetic field.
The magnetic force is the only force, if any, acting on the particle. Describe the trajectory of the
particle assuming that it remains in the uniform magnetic field, and, that it's elevation does not
change. - CORRECT ANSWER The particle will travel counterclockwise, as viewed from
above, around a horizontal circle.
The radius of curvature of the path of a charged particle in a uniform magnetic field is directly
proportional to: - CORRECT ANSWER the particle's momentum
A positively charged particle moves in the positive x direction in a uniform magnetic field pointing in
the negative z direction. You want to balance the magnetic force with an electric field so that the
particle will continue moving along a straight line. The electric field should point in the... -
CORRECT ANSWER negative y direction
QUESTIONS AND CORRECT ANSWERS
The voltage across each capacitor in a set of capacitors in series is... - CORRECT
ANSWER inversely proportional to its capacitance
A capacitor is connected to a battery. When a dielectric is inserted between the plates of the
capacitor... - CORRECT ANSWER both the capacitance and the charge change
The electric potential inside a capacitor... - CORRECT ANSWER increases linearly from the
negative to the positive plate.
Two identical capacitors A and B are connected in parallel with each other across a battery. If mica (of
dielectric constant 5.4) is inserted in B: - CORRECT ANSWER B will have the larger charge
A parallel plate capacitor is connected to a battery and charged to voltage V. Leah says that the charge
on the plates will decrease if the distance between the plates is increased while they are still connected
to the battery. Gertie says that the charge will remain the same. Which one, if either, is correct, and
why? - CORRECT ANSWER Leah, because the capacitance decreases when the plate
separation is increased.
If the area of the plates of a parallel plate capacitor is doubled, the capacitance is... - CORRECT
ANSWER doubled
Consider a pair of two identical capacitors. In which case is the capacitance of the pair greater? -
CORRECT ANSWER When they are connected in parallel with each other.
In a loop in a closed circuit, the sum of the currents entering a junction equals the sum of the currents
leaving a junction because... - CORRECT ANSWER charge is neither created nor destroyed at
a junction.
The algebraic sum of the changes of potential around any closed circuit loop is... - CORRECT
ANSWER zero
, The battery is disconnected from a series RC circuit after the capacitor is fully charged and is replaced
by an open switch. When the switch is closed... - CORRECT ANSWER the capacitor does not
allow current to pass.
Consider a capacitor which is charged to 12 volts and then connected across a resistor. Let t1/2 be the
time it takes for the voltage to drop down to 6 volts. Suppose the experiment is repeated, but with a
pair of capacitors connected in parallel with each other in place of the original capacitor, where each
element of the pair has the same capacitance as the original capacitor. How does the new t1/2 compare
with the original t1/2? - CORRECT ANSWER The new t1/2 is twice the original t1/2.
A junior Thomas Edison wants to make a brighter light bulb. He decides to modify the filament. How
should the filament of a light bulb be modified in order to make the light bulb produce more light at a
given voltage? - CORRECT ANSWER increase the diameter only
An electron moving in the positive x direction experiences a magnetic force in the positive z direction.
If Bx = 0, what is the direction of the magnetic field? - CORRECT ANSWER negative y
direction
A positively-charged particle is moving southward in a downward-directed uniform magnetic field.
The magnetic force is the only force, if any, acting on the particle. During the next few centimeters of
its travel... - CORRECT ANSWER the particle keeps on going at the same speed.
A positively-charged particle is moving southward in a downward-directed uniform magnetic field.
The magnetic force is the only force, if any, acting on the particle. Describe the trajectory of the
particle assuming that it remains in the uniform magnetic field, and, that it's elevation does not
change. - CORRECT ANSWER The particle will travel counterclockwise, as viewed from
above, around a horizontal circle.
The radius of curvature of the path of a charged particle in a uniform magnetic field is directly
proportional to: - CORRECT ANSWER the particle's momentum
A positively charged particle moves in the positive x direction in a uniform magnetic field pointing in
the negative z direction. You want to balance the magnetic force with an electric field so that the
particle will continue moving along a straight line. The electric field should point in the... -
CORRECT ANSWER negative y direction
