ConcepTest 17.1aConcepTest 17.1a Electric Potential Energy I Electric Potential Energy I 1) proton

2) electron

3) both feel the same force

4) neither – there is no force

5) they feel the same magnitude force but opposite direction

E

electronelectron

protonproton

E

electronelectron

protonproton++

--

A A protonproton and an and an electronelectron are in are in a constant electric field created a constant electric field created by oppositely charged plates. by oppositely charged plates. You release the You release the protonproton from from the the positivepositive side and the side and the electronelectron from the from the negativenegative side. side. Which feels the larger electric Which feels the larger electric force?force?

E

electronelectron

protonproton

E

electronelectron

protonproton++

--

1) proton

2) electron

3) both feel the same acceleration

4) neither – there is no acceleration

5) they feel the same magnitude acceleration but opposite direction

A A protonproton and an and an electronelectron are in are in a constant electric field created a constant electric field created by oppositely charged plates. by oppositely charged plates. You release the You release the protonproton from from the the positivepositive side and the side and the electronelectron from the from the negativenegative side. side. Which has the larger Which has the larger acceleration?acceleration?

ConcepTest 17.1bConcepTest 17.1b Electric Potential Energy II Electric Potential Energy II

E

electronelectron

protonproton

E

electronelectron

protonproton++

--

1) proton

2) electron

3) both acquire the same KE

4) neither – there is no change of KE

5) they both acquire the same KE but with opposite signs

ConcepTest 17.1cConcepTest 17.1c Electric Potential Energy III Electric Potential Energy III

A A protonproton and an and an electronelectron are in are in a constant electric field created a constant electric field created by oppositely charged plates. by oppositely charged plates. You release the You release the protonproton from from the the positivepositive side and the side and the electronelectron from the from the negativenegative side. side. When it strikes the opposite When it strikes the opposite plate, which one has more KE?plate, which one has more KE?

Which two points have Which two points have the the samesame potential? potential?

1) A and C

2) B and E

3) B and D

4) C and E

5) no pair

A

C

B DEQ

ConcepTest 17.6ConcepTest 17.6 Equipotential of Point ChargeEquipotential of Point Charge

ConcepTest 18.1ConcepTest 18.1 Connect the Battery Connect the Battery

Which is the correct way to Which is the correct way to

light the lightbulb with the light the lightbulb with the

battery?battery?

4) all are correct

5) none are correct

1) 3)2)

1) Ohm’s law is obeyed since the current Ohm’s law is obeyed since the current still increases when V increasesstill increases when V increases

2) Ohm’s law is not obeyedOhm’s law is not obeyed

3) This has nothing to do with Ohm’s lawThis has nothing to do with Ohm’s law

ConcepTest 18.2ConcepTest 18.2 Ohm’s Law Ohm’s Law

You double the You double the voltagevoltage

across a certain conductor across a certain conductor

and you observe the and you observe the currentcurrent

increases three times. What increases three times. What

can you conclude?can you conclude?

ConcepTest 18.3aConcepTest 18.3a Wires IWires I

Two wires, Two wires, AA and and BB, are made of the , are made of the

same metalsame metal and have and have equal lengthequal length, ,

but the resistance of wire but the resistance of wire AA is is four four

timestimes the resistance of wire the resistance of wire BB. How . How

do their diameters compare?do their diameters compare?

1) ddAA = 4 = 4 ddBB

2) ddAA = 2 = 2 ddBB

3) ddAA = = ddBB

4) 4) ddAA = 1/2 = 1/2 ddBB

5) 5) ddAA = 1/4 = 1/4 ddBB

ConcepTest 18.3bConcepTest 18.3b Wires II Wires II

A wire of resistance A wire of resistance RR is is

stretched uniformly (keeping its stretched uniformly (keeping its

volume constant) until it is twice volume constant) until it is twice

its original length. What happens its original length. What happens

to the resistance?to the resistance?

1) it decreasesit decreases by a factor 4by a factor 4

2) it decreasesit decreases by a factor 2by a factor 2

3) it stays the sameit stays the same

4) it increases4) it increases by a factor 2by a factor 2

5) it increases5) it increases by a factor 4by a factor 4

ConcepTest 18.4ConcepTest 18.4 Dimmer Dimmer

When you rotate the knob of a When you rotate the knob of a

light dimmer, what is being light dimmer, what is being

changed in the electric circuit?changed in the electric circuit?

1) the power

2) the current

3) the voltage

4) both (1) and (2)

5) both (2) and (3)

ConcepTest 18.5aConcepTest 18.5a LightbulbsLightbulbs

Two lightbulbs operate at 120 V, but one Two lightbulbs operate at 120 V, but one

has a power rating of has a power rating of 25 W25 W while the while the

other has a power rating of other has a power rating of 100 W100 W. .

Which one has the greater resistance? Which one has the greater resistance?

1) the 25 W bulb

2) the 100 W bulb

3) both have the same

4) this has nothing to do with resistance

ConcepTest 18.5bConcepTest 18.5b Space Heaters ISpace Heaters I

Two space heaters in your living Two space heaters in your living

room are operated at 120 V. room are operated at 120 V.

Heater 1 has Heater 1 has twicetwice the resistance the resistance

of heater 2. Which one will give of heater 2. Which one will give

off more heat?off more heat?

1) heater 1

2) heater 2

3) both equally

ConcepTest 19.1aConcepTest 19.1a Series Resistors ISeries Resistors I

9 V

Assume that the voltage of the battery Assume that the voltage of the battery

is is 9 V9 V and that the three resistors are and that the three resistors are

identicalidentical. What is the potential . What is the potential

difference across each resistor?difference across each resistor?

1) 12 V

2) zero

3) 3 V

4) 4 V

5) you need to know the actual value of R

ConcepTest 19.1bConcepTest 19.1b Series Resistors IISeries Resistors II

12 V

R1= 4 R2= 2

In the circuit below, what is the In the circuit below, what is the

voltage across voltage across R1??

1) 12 V

2) zero

3) 6 V

4) 8 V

5) 4 V

ConcepTest 19.2aConcepTest 19.2a Parallel Resistors IParallel Resistors I

In the circuit below, what is the In the circuit below, what is the

current through current through R1??

10 V

R1= 5

R2= 2

1) 10 A

2) zero

3) 5 A

4) 2 A

5) 7 A

ConcepTest 19.2bConcepTest 19.2b Parallel Resistors IIParallel Resistors II

1) increases

2) remains the same

3) decreases

4) drops to zero

Points P and Q are connected to a Points P and Q are connected to a

battery of fixed voltage. As more battery of fixed voltage. As more

resistors resistors RR are added to the parallel are added to the parallel

circuit, what happens to the circuit, what happens to the total total

currentcurrent in the circuit? in the circuit?

ConcepTest 19.3aConcepTest 19.3a Short CircuitShort Circuit

Current flows through a Current flows through a

lightbulb. If a wire is now lightbulb. If a wire is now

connected across the connected across the

bulb, what happens?bulb, what happens?

1) all the current continues to flow through all the current continues to flow through the bulbthe bulb

2) half the current flows through the wire, half the current flows through the wire, the other half continues through the the other half continues through the bulbbulb

3) all the current flows through the wire all the current flows through the wire

4) none of the abovenone of the above

ConcepTest 19.3bConcepTest 19.3b Short Circuit IIShort Circuit II

Two lightbulbs A and B are Two lightbulbs A and B are

connected in series to a connected in series to a

constant voltage source. constant voltage source.

When a wire is connected When a wire is connected

across B, bulb A will:across B, bulb A will:

1) glow brighter than beforeglow brighter than before

2) glow just the same as beforeglow just the same as before

3) glow dimmer than beforeglow dimmer than before

4) go out completely4) go out completely

5) explode5) explode

ConcepTest 19.4aConcepTest 19.4a Circuits ICircuits I

1) circuit 1circuit 1

2) circuit 2circuit 2

3) both the sameboth the same

4) it depends on it depends on RR

The lightbulbs in the circuit below The lightbulbs in the circuit below

are identical with the same are identical with the same

resistance resistance RR. Which circuit . Which circuit

produces more light? (brightness produces more light? (brightness

power) power)

ConcepTest 19.4bConcepTest 19.4b Circuits IICircuits II

1) twice as muchtwice as much

2) the samethe same

3) 1/2 as much1/2 as much

4) 1/4 as much 1/4 as much

5) 4 times as much 4 times as much

10 V10 V

A

B C

The three lightbulbs in the circuit all have The three lightbulbs in the circuit all have

the the same resistance ofsame resistance of 1 1 By how By how

much is the much is the brightness of bulb B brightness of bulb B greater greater

or smaller than the or smaller than the brightness of bulb Abrightness of bulb A? ?

(brightness (brightness power) power)

ConcepTest 19.7ConcepTest 19.7 Junction RuleJunction Rule

1) 2 A

2) 3 A

3) 5 A

4) 6 A

5) 10 A

5 A

8 A

2 A

P

What is the current in branch P?What is the current in branch P?