PHY 1409 Book MisConceptual Questions Ch 16-30

which of the following is a vector? -electric potential -electric potential energy -electric field -equipotential lines -capacitance

-electric field

which are the worst places to be in a lightning storm

-in the middle of a grassy meadow -next to a tall tree in the forest -on a metal observation tower

which of the following do not affect the capacitance? -area of the plates -separation of the plates -material between plates -charge on the plates -energy stored in the capacitor

-material between the plates and -charge on the plates

two identical 10 V batteries and two identical 10 ohm resistors are placed in series are shown in the figure. if a 10 ohm lightbulb is connected with one end connected between the batteries and 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

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 three +q point charges from infinity to a distance d apart from each other?

3W

the capacitor is the circuit shown in the figure 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 to 1/2 Q how long does it take to drop to 1/4 Q?

4.0 seconds

in which circuits shown in this figure are resistors connected in series?

A and C

a current in a wire points into the page as shown. in which direction is the magnetic field at point B?

B

a current in a wire points into the page as shown. in which direction is the magnetic field at point A?

C

four identical point charges are placed near each other. at the point halfway between the two charges

E = 0, V ≠ 0

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 restore in this figure are connected in parallel?

R1 & R3

which resistor shown in the figure has the greatest current going through it? assume that all resistors are equal

R5

indicate which of the following will reduce a magnetic field -a magnet -the earth -an electric charge at rest -a moving electric charge -an electric current -the voltage of a battery not connected to anything -an ordinary piece of iron -a piece of any metal

a magnet the Earth a moving electric charge an electric current

which statements about the force on a charged particle placed in a magnetic field are true?

a magnetic force is exerted only if the particle is moving

the unit kilowatt-hour is a measure of

an amount of energy

a nonconducting plastic hoop is held in a magnetic field that points out of the page. as the strength of the field increases

an induced emf will be produced but no current

a square loop moves to the right from an area when B = 0, completely through a region containing a uniform magnetic field directed into the page and then out to B = 0 at point L. a current is induced in the loop

as it passes line J or line L

where in the circuit of the figure is the current the largest?

at point c

when a proton (Q = +e) and an electron (Q = -e) are in a constant electric field created by oppositely charged plates, and they strike the opposite plate, which one has more kinetic energy?

both acquire the same kinetic energy

as a proton moves through space, it creates

both an electric field and magnetic field

this figure shows 3 identical bulbs in a current. what happens to the brightness of bulb A if you replace bulb B its a short circuit?

bulb a goes out

Q1 = -0.10 is located on the positive x axis at x=1.0m. Q2= +0.10 uc is located at the origin. which of the following is true of the force on Q1 due to Q2?

it changes from the +x direction to the -x direction

which vector best represents in the direction of the electric field at the fourth corner of the square due to the three charges shown

d)

as an object acquires a positive charge, its mass usually

decreases

a battery establishes a voltage V on a parallel-plate capacitor. after the batter is disconnected, the distance between the plates is doubled without loss of charge. accordingly, the capacitance _____________ and the voltage between the plates _____________

decreases; increases

as a capacitor is being charged in an RC circuit, the current flowing through the resistor is

decreasing

Q1= -0.10 uc is located at the origin. Q2 = +0.10 uc is located on the positive x axis at x = 1.0m. which of the following is true of the force on Q1 due to Q2?

it is attracted and directed in the + x direction.

which of the following statements is false? the magnetic field of a current-carrying wire ...

exists only if the current in the wire is changing

two lops of wire are moving in the vicinity of a very long straight wire carrying a steady current. find the direction of the induced current in each loop

for C: clockwise for D: zero

which of the following statements is valid?

if the potential throughout a particular region is constant, the field throughout that region must be zero

to be safe during a lightening storm, it is best to be

inside a metal car

a proton enters a uniform magnetic field that is perpendicular to the proton's velocity. what happens to the kinetic energy of the proton?

it stays the same

when the switch shown is closed, what will happen to the voltage across resistor R1?

it will increase

when the switch shown in the figure is closed, what will happen to the voltage across resistor R4?

it'll decrease

we wish to determine the electric field at a point near a positively charged metal sphere (good conduction). we do so by brining a small positive test charge, q0, to this point and measure the force, F0, on it. F0/q0 will be _____________ and the electric field E 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 capacitor 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 heart rate when the patient is exercising, which statement below is true? the capacitor...

needs to discharge faster, so the resistance should be increased

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 a) some of the charge is used up by the resistor b) some of the current is used up by the resistor

neither a) nor b) is true

electrons carry energy from a battery to a lightbulb. what happens to the electrons when the reach the lightbulb? -the electrons are used up -the electrons stay in the lightbulb -the electrons are emitted as light -fewer electrons leave the bulb than enter it -none of the above

none of the above

which of the following statements about the force on a charged particle due to a magnetic field are not valid? -it depends on the particle's charge -it depends on the particle's velocity -it depends on the strength of the external magnetic field -it acts at right angles to the direction of the particle's motion - none of the above

none of the above; all statements are valid

which of the following statements about Ohm's law are true?

ohm's law relates the current through a wire to the voltage across the wire

for a charged particle, a constant magnetic field can be used to change

only the direction of the particle's velocity

if the two charged plates were moved until they are half the distance shown without changing the charge on the plates, the electric field near the center of the plates would

remain almost exactly the same

when a charged particle moves parallel to the direction of a magnetic field, the particle travels in a ...

straight line

for the circuit shown, what happens when the switch S is closed?

the capacitor eventually charges up to the full battery emf at a rate determined by R and C

why might a circuit breaker open if you plug too many electrical devices into a single circuit

the current becomes too high

a +0.2 uC charge is in an electric field. what happens if that charge is replaced by a +0.4 uC charge?

the elastic potential doubles, but the electric potential energy stays the same

two identical positive charges are placed near each other. at the point halfway between the two charges

the electric field is not zero and the potential is zero

a +0.2 uC charge is in an electric field. what happens if that charge is replaced by a -0.2 uC charge?

the electric potential stays the same, but the electric potential energy changes sign

when a light switch is turned on, the light comes on immediately because

the electrons already in the wire are instantly "pushed" by a voltage difference

the figure 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 in the opposite direction to the field

a proton (Q = +e) and an electron (Q = -e) 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 electron force?

the magnitude of the force is the same for both but in opposite directions

if ammeters and voltmeters are not to significantly alter the quantities they are measuring

the 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

when a battery is connected to a lightbulb properly, current flows through the lightbulb and makes it glow. how much current flows through the batter compared with the lightbulb?

the same amount

why is an appliance cord with a three-prong plug safer than one with two prongs?

the third prong grounds the case, so the case cannot reach a high voltage

two parallel wires are vertical. the one on the left carries a 10A current upward. the other carries 5A current downward. compare the magnitude of the force that each wire exerts on the other.

the two wires exert the same force on each other

if there is induced current in question 18 (figure 21-51) wouldn't that cost energy? where would that energy come from in case a)

there is less kinetic energy

nothing happens when birds land on a power line, yet we are warned not to touch a power line with a ladder. what's different?

there is little to no voltage drop between a bird's 2 feet, but there's a significant voltage drop between the top of a ladder touching a power line and the bottom of the ladder on the ground

Fred the lightening bug has a mass m and a charge +q. Jane, his lightning-bug wife, has a mass of 3/4 m and a charge of -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

a wire carries a current directly away from you. which way do the magnetic field lines produced by this wire point?

they make circles around the wires

a coil rests in the plane of the page while a magnetic field is directed into the page a clockwise current is induced

when the size of the coil decreases when the magnetic field is tilted so it is no longer perpendicular to the page

when connected to a battery, a lightbulb glows brightly. if the battery is revised and reconnected to the bulb, the bulb with glow...

with the same brightness

a wire loop moves at constant velocity without rotation through a constant magnetic field. the induced current in the loop will be

zero