Download Circuits - Pretty Good Physics

Circuits
Created by Craig Smiley (Harrison HS, West Lafayette, IN)
Supported by grant PHY-0851826
from the National Science Foundation
and by Purdue University
Lesson 1 – Ohm’s Law
Simple Circuit
Jumper cables
Simplified Model of a Battery
According to this model of a battery, which
illustration would show a “dead” battery?
A.
B.
C.
D. None of these
• Chemical Reaction
Rechargeable Battery
When you are “recharging” a rechargeable battery,
what is going on?
A. More electrons are being added to the battery
(kind of like filling up your gas tank with more
gasoline) giving it more charge.
B. The chemical reaction is made to reverse
sending the electrons back over to the negative
side giving it more energy.
C. Both of these
D. Neither of these
Current
What does current measure?
A. How fast the electrons are flowing past a
certain point.
B. How many electrons are flowing past a
certain point in one second.
C. Both of these
D. Neither of these
Speed of Electron
You turn on a light switch and the light comes on. How
fast do electrons travel through the wire?
A. It is instantaneous (infinite speed)
B. The speed of light
C. Not quite the speed of light, but close
D. Really slow
Current
Which way is current flowing around this
circuit?
A. Clockwise
B. Counter-clockwise
C. Both A & B
D. Neither A or B
E. Can’t be determined
Voltage & Current
Cause and Effect: what causes what?
A. Voltage causes Current
B. Current causes Voltage
C. They cause each other (the chicken & the egg)
D. Neither cause the other
Current
Rank the amount of current at different points
around the circuit, from greatest to least.
A. 1 > 2 > 3 > 4 > 5
B. 1 = 2 > 3 > 4 = 5
C. 1 = 5 > 2 = 4 > 3
D. 1 = 2 = 3 = 4 = 5
E. None of these
Electrons
What happens to the electrons once they get to
filament?
A. They are converted into light
(the electrons are consumed)
B. They slow down
C. They lose electric potential energy
D. Two of these (A-C)
E. All of these (A-C)
Potential Drop
A “potential drop” or a “voltage drop” is a
section of a circuit where energy is used, causing
the electric potential to decrease across two
different points along the circuit. Between what
two points is there the biggest potential drop?
A. Across A to B
B. Across B to C
C. Across C to D
D. Across D to A
Potential Gain
A “potential gain” or a “voltage gain” is a section
of a circuit where energy is given, causing the
electric potential to increase across two
different points along the circuit. Between what
two points is there the biggest potential gain?
A. Across A to B
B. Across B to C
C. Across C to D
D. Across D to A
Incandescent Light Bulbs
In an incandescent light bulb is a filament, which
is a really skinny piece of wire (made of tungsten)
that is wrapped in tight coils. Which had more
resistance in your circuit, the thicker copper wire
or the filament?
A. Thick wire
B. Skinny filament
C. Both had the same
D. Neither had resistance
E. Can’t be determined
Incandescent Light Bulbs
At first the circuit is open and the light bulb is off and then the
circuit is closed and the light bulb turns on. During the first
few seconds, what happens to the temperature of the
filament, and what happens to the filament’s resistance
because of that?
A. The temperature of the filament increases causing its
resistance to increase
B. The temperature of the filament increases causing its
resistance to decrease
C. The temperature of the filament decreases causing its
resistance to increase
D. The temperature of the filament decreases causing its
resistance to decrease
E. The temperature of the filament doesn’t change and the
resistance stays the same.
Outlets
Probably all of the exposed outlets around your
house are rated at 120V. What does that mean?
A. 120V will come out if you complete the circuit
by plugging something in.
B. 120V is the rate at which electrical energy will
be used if you plugged something in.
C. 120V is the difference of the electric potential
from one hole of the outlet to the other.
D. Two of these
E. None of these
Getting Shocked
When power lines say HIGH VOLTAGE!, why is
that dangerous if you touched it?
A. A lot of Voltage would flow through you
B. A lot of Current would flow through you
C. A lot of both Voltage and Current would flow
through you
D. None of these
Getting Shocked
Why can birds sit on a power line and not get
fried?
A. They are not touching the ground
B. There is not a difference in electric potential
across their feet
C. They are only holding on to one wire
D. Two of these (A-C)
E. All of these (A-C)
Dimmer Switch
One of your lamps has a dimmer switch on it.
As you turn the dimmer switch up, making the
light brighter, what changes occur in these
measurements for the entire circuit?
A. ΔV:same
R:↑
I:↑
B. ΔV:same
R:↓
I:↑
C. ΔV:↑
R:↓
I:↑
D. ΔV:↑
R:↓
I:same
E. None of these
Short Circuit
What happened if the circuit is wired this
way and why?
A. The wire will get hot because the
Voltage is high
B. The wire will get hot because the
Current is high
C. The wire will get hot because both
the Voltage and Current are high
D. Nothing because there is no Voltage
E. Nothing because there is no Current
Simple Circuit
What changes would occur in these
measurements for the entire circuit
if you changed the short circuit to
now include the light bulb?
A. ΔV:↑
R:↑
I:↑
B. ΔV:↑
R:↑
I:same
C. ΔV:same
R:↓
I:↑
D. ΔV:↓
R:↑
I:↓
E. None of these
Jumper Cables
Why was I not shocked with the jumper cables?
A. My head had too much resistance so the voltage
wasn’t strong enough to cause a substantial
current.
B. My head had too much resistance so the current
wasn’t strong enough to cause a substantial
voltage.
C. My head decreased the voltage so there wasn’t a
substantial current.
D. My head decreased the current voltage so there
wasn’t substantial current.
E. None of these
Short Circuit
What happens if you had the simple circuit and
then you added an additional wire to it as shown
below. What would happen to the light bulb?
A.
B.
C.
D.
It would stay on just as bright
It would stay on, but ½ as bright
It would turn off
None of these
Lesson 2 - Power
4 Light Bulbs
Power
Which light bulb is going to be brighter when
plugged into a 120V outlet?
A. 60 W
B. 100 W
C. Same
D. Can’t be determined
Power
Which would be the correct equation for Power
that would incorporate only current and
resistance after combining ΔV=IR and P=IΔV?
A. 𝑃 = 2𝐼𝑅
B. 𝑃 = 𝐼2 𝑅
C. 𝑃 = (𝐼𝑅)2
D. 𝑃 =
1
𝑅
E. None of these
Power
Which would be the correct equation for Power
that would incorporate only voltage and
resistance after combining ΔV=IR and P=IΔV?
A. 𝑃 =
(∆𝑉)2
𝑅
B. 𝑃 = (∆𝑉)2 𝑅
C. 𝑃
D. 𝑃
𝑅
=
(∆𝑉)2
1
=
𝑅
E. None of these
Power
(∆𝑉)2
,
𝑅
Based off of 𝑃 =
what would cause the Power of an
appliance to increase?
i.
ii.
iii.
iv.
A.
B.
C.
D.
E.
If voltage stayed the same and resistance increased
If voltage stayed the same and resistance decreased
If resistance stayed the same and voltage increased
If resistance stayed the same and voltage decreased
i & iii
i & iv
ii & iii
ii & iv
None of these
Power
Based off of the equation P=I2R, which would
cause a greater increase in Power?
A. If current stayed the same and resistance increased
by a certain amount
B. If resistance stayed the same and current increased
by the same certain amount
C. Both would have the same effect
D. Can’t be determined
Power
In a simple circuit where a resistor is connected
to a battery, what would happen to the Power
dissipated by the resistor if the resistance of the
resistor was increased?
A. Increase
B. Decrease
C. Stay the same
D. Can’t be determined
Power
You have a simple flashlight circuit with a single
6 V battery. You try two different bulbs. Bulb #1
glows brightly. Bulb #2 glows dimly. Which bulb
has the larger resistance? (The brightness is an
indicator of Power dissipated by light bulb.)
A. Bulb #1
B. Bulb #2
C. Can’t be determined
Electric Bill
What do Electric Companies sell us?
A. Power
B. Energy
C. Current
D. Voltage
E. All of these
Lesson 3 – Series
Discovery with Christmas tree lights
Series
Rank the amount of current at these locations
around this series circuit from greatest to least.
A. 1 > 2 > 3 > 4 > 5
B. 1 > 2 > 3 = 4 > 5
C. 1 > 5 > 2 > 3 = 4
D. 5 > 1 > 4 > 2 = 3
E. 1 = 2 = 3 = 4 = 5
Series
If one of the resistors was taken away, what
would happen to the current coming from the
battery?
A. Current would decrease
B. Current would stay the same
C. Current would increase
D. Can’t be determined
Series
What is the current going through the 4Ω
resistor if the circuit is hooked up to a 24V
battery?
A. 2 A
B. 6 A
C. 8 A
D. Can’t be determined
E. None of these
Series
What is the potential drop across the 4Ω resistor
if the circuit is hooked up to a 24V battery?
A. 2 V
B. 6 V
C. 8 V
D. Can’t be determined
E. None of these
Series
Which resistor has the greatest potential drop
across it?
A. 3 Ω
B. 5 Ω
C. 4 Ω
D. All have the same
E. Can’t be determined
Series
If these resistors were light bulbs, rank the order
of brightness, from bright to dim. The brightness
is indicator of the Power dissipated.
A. 5 > 4 > 3
B. 3 > 4 > 5
C. 3 > 5 > 4
D. 3 = 5 = 4
E. Can’t be determined
Series
What is the Power dissipated by the entire
circuit?
A. 2 W
B. 36 W
C. 48 W
D. Can’t be determined
E. None of these
Lesson 4 – Parallel Circuits
Day 1 – Christmas tree light discovery
Day 2 – Fuses
Parallel
If another resistor was added in parallel, what
would happen to the voltage across the 80Ω
resistor?
A. Increase
B. Stay the same
C. Decrease
D. Can’t be determined
Kirchhoff’s Loop Rule
Parallel
Which resistor has the most current flowing
through it?
A. 70 Ω
B. 90 Ω
C. 80 Ω
D. All have the same
E. Can’t be determined
Parallel
If these resistors were light bulbs, rank the order
of brightness, from bright to dim. The brightness
is indicator of the Power dissipated.
A. 70 > 80 > 90
B. 90 > 80 > 70
C. 80 > 90 > 70
D. 80 = 90 = 70
E. None of these
Parallel
How much current is going through the 2Ω and
3Ω resistor respectively?
A. 6A & 4A
B. 1/6 A & 1/4 A
C. Both have 12/5 A
D. Both have 24/5 A
E. Both have 72/5 A
Parallel
What is the total current coming from the
battery?
A. 12/5 A
B. 5 A
C. 6 A
D. 4 A
E. 10 A
Water Tower Analogy
If you put another hole in the water tower and
added another pipe with kinks in it, what would
happen to the rate at which water draining from
the water tower?
A. Increasing
B. Decreasing
C. Staying the same
D. Can’t be determined
Parallel
If another resistor was added in parallel, what
would happen to the total current?
A. Increase
B. Stay the same
C. Decrease
D. Can’t be determined
Kirchhoff’s Loop Rule
Parallel
If another resistor was added in parallel, what
would happen to the equivalent (total)
resistance of the circuit?
A. Increase
B. Stay the same
C. Decrease
D. Can’t be determined
Parallel
Rank which point has the most current flowing
through it, from greatest to least.
A. 1 > 3 > 2
B. 1 > 2 > 3
C. 3 > 2 > 1
D. 1 = 2 = 3
E. None of these
Kirchhoff’s Junction Rule
Parallel
Rank which point has the most current flowing
through it, from greatest to least.
A. 1 > 3 > 2 > 4 > 5
B. 1 > 3 > 4 > 2 > 5
C. 1 > 3 = 4 > 2 > 5
D. 1 = 5 > 3 = 4 > 2
E. None of these
Parallel
Rank which point has the most current flowing
through it, from greatest to least.
A. 1 = 5 > 2 = 4 > 3
B. 3 > 1 = 5 > 2 = 4
C. 5 > 4 > 3 > 1 > 2
D. 5 > 3 > 1 > 4 > 2
E. None of these
Parallel
If another resistor was added in parallel, what
would happen to the current being drawn from
the battery (point 2 compared to point 1)?
A. Increase
B. Stay the same
C. Decrease
D. Can’t be determined
House Wiring
How are the appliances in your house wired?
A. Series
B. Parallel
Lesson 5 – Combination Circuits
Unscrew light bulbs
Combination Circuits
Which of these schematic diagrams represent the same circuit?
A.
B.
C.
D.
E.
F.
1&2
1&3
1&4
2&3
1, 2, & 3
1, 2, & 4
The 6Ω resister has 2A of current flowing
through it. How much current is flowing
through the 4Ω resistor?
A.
B.
C.
D.
E.
4/3 A
2A
3A
6A
12 A