EXAM 1 Misconceptual questions
two identical 10V batteries and two identical 10 ohm resistors are placed in series as shown in fig 19-42. if a 10 ohm lightbulb is connected with one end connected between the batteries and the other end between the resistors, how much current will flow through the lightbulb?
0 A
a 10,000 ohm resistor is placed in series with a 100 ohm resistor. the current in the 10,000 ohm resistor is 10 A. if the resistors are swapped, how much current flows through the 100 ohm resistor?
10 A
which of the following do not affect capacitance?
charge on the plates and energy stored in the capacitor
which of the following is a vector?
electric field
if it takes an amount of work W to move two +q point charges from infinity to a distance d apart from each other, then how much work should it take to move 3 +q point charges from infinity to a distance d apart from each other?
3W
The capacitor in the circuit shown in Fig. 19-47 is charged to an initial value Q. When the switch is closed, it discharges through the resistor. It takes 2.0 seconds for the charge to drop 1/2Q. How long does it take to drop to 1/4Q?
4 sec
four identical point charges are arranged at the corners of a square. the electric field E and potential V at the center of the square are
E=0 V does not equal zero
which resistors in fig 19-41 are connected in parallel?
R1 and R3
which resistor shown in fig 19-43 has the greatest current going through it?
R5
Why is an appliance cord with three prong plug safer than one with 2 prongs?
The third prong grounds the case, so the case cannot reach a high voltage.
in which circuits shown in fig 19-40 are resistors connected in series?
a and c are in series
the unit kWh is a measure of
an amount of energy
when the proton and electron in the previous question strike the opposite plate, which one has more kinetic energy?
both acquire the same kinetic energy
fig 19-44 shows three identical bulbs in a circuit. what happens to the brightness of bulb a if you replace bulb b with a short circuit
bulb A goes out
for the circuit shown in fig 19-46, what happens when the switch S is closed?
capacitor eventually charges up to full battery emf at a rate determined by R and C
which vector best represents the direction of the electric field at the fourth corner of the square due to the three charges shown in fig. 16-51
d
when the switch shown in fig 19-45 is closed, what will happen to the voltage across resistor R4? it will
decrease
as an object acquires a positive charge, its mass usually
decreases
a battery established a voltage V on a parallel plate capacitor. after the battery is disconnected, the distance between the plates is doubled without loss of charge. accordingly, the capacitance_____ and the voltage btwn the plates_____.
decreases; increases
as a capacitor is being charged in an RC circuit, the current flowing through the resistor is
decreasing
which of the following statements is valid?
if the potential throughout a particular region is constant, the field throughout that region must be zero
which are the worst places to be during a lightning storm?
in the middle of a grassy meadow next to a tall tree in a forest on a metal observation tower
when the switch shown is closed, what will happen to the voltage across resistor R1? It will
increase
to be safe during a lightning storm, it is best to be
inside a metal car
swap the positions of q1 and q2 of the previous question. which of the following is true of the force on q1 due to q2?
it changes from the + x direction to the - x direction
Q1=-0.1mC is located at the origin. Q2= +0.1mC is located on the positive x axis at x-1 m. which of the following is true of the force on Q1 due to Q2?
it is attractive and directed in the + x direction
where in the circuit is the current the largest? or is it the same in all points?
it is the same at all points
we wish to determine the electric field at a point near a positively charged metal sphere. we do so by bringing a small positive test charge, q0, to this point and measure the force F0 on it. F0/q0 will be ______ the electric field as it was at that point before the test charge was present
less than
When the capacitors are connected in series, the effective capacitance is ___________ the smallest capacitance; when capacitors are connected in parallel, the effective capacitance is _____________ the largest capacitance.
less than; greater than
we are usually not aware of the electric force acting between two everyday objects because
most everyday objects have as many plus charges as minus charges
A resistor and a capacitor are used in series to control the timing in the circuit of a heart pacemaker. To design a pacemaker that can double the HR when the patient is exercising, which statement below is true? The capacitor...
needs to discharge faster, so the resistance should be decreased
a small metal ball hangs from the ceiling by an insulating thread. the ball is attracted to a positively charged rod held near the ball. the charge of the ball must be
negative or neutral
when current flows through a resistor,
neither is true
electrons carry energy from a battery to a lightbulb. what happens to the electrons when they reach the lightbulb?
none of the options
when you double the voltage across a certain material or device, you observe that the current increases by a factor of 3, what can you conclude?
ohm's law is NOT obeyed in this case
which of the following statements about ohm's law is true?
ohm's law relates the current through a wire to the voltage across the wire
refer to firgure 16-32d. if the two charged plates were moved until they are half distance shown without changing the charge on the plates, the electric field near the center of the plates would
remain almost exactly the same
if ammeters and voltmeters are not to significantly alter the quantities they are measuring,
resistance of an ammeter should be much lower, and the resistance of a voltmeter should be much higher, than those of the circuit being measured
why might a circuit breaker open if you plug too many electrical devices into a single circuit?
the current becomes too high
two identical positive charges are placed near each other...
the electric field is in zero and the potential is positive
a +0.2 mC charge is in an electric field. what happens if that charge is replaced by a -0.2 mC charge?
the electric potential stays the same but the electric potential energy changes sign
a +0.2 mC charge is in an electric field. what happens if that charge is replaced by a +0.4 mC charge?
the electric potential stays the same but the electric potential energy doubles
when a light switch is turned on, the light comes on immediately because
the electrons in the wire are instantly pushed by a voltage difference
figure 16-50 shows electric field lines due to a point charge. what can you say about the field at point 1 compared with the field at point 2?
the field at point 1 is larger because the field lines are closer together in that region
a negative point charge is in an electric field created by a positive point charge. which of the following is true?
the field points away from the positive charge and the force on the negative charge is on the opposite direction to the field
a proton and an electron are in a constant electric field created by oppositely charged plates. you release the proton from near the positive plate and the electron from near the negative plate, which feels the larger electric force?
the magnitude of the force is the same for both but in opposite directions
when a battery is connected to a lightbulb properly, current flows through the lightbulb and makes it glow. how much current flows through the battery compared with the lightbulb?
the same amount
nothing happens when birds land on a power line, yet we are warned not to touch a power line with a ladder. what is the difference?
there is little to no voltage drop between the top of a ladder touching the power line and at the bottom of the ladder on the ground
fred the lightning bug has a mass M and a charge +q. jane, his lightning bug wife, has a mass of 3/4M and a charge -2q. because they have charges of opposite sign, they are attracted to each other. which is attracted more to the other and by how much?
they are attracted to each other by the same amount
when connected to a battery, a lightbulb glows brightly. if the battery is reversed and reconnected to the bulb, the bulb will glow
with the same brightness
