MS-PS2-3: Asking Questions About Electric and Magnetic Force Data
In plain English: MS-PS2-3 is the NGSS middle school performance expectation that asks students to ask questions about data to find the factors that affect the strength of electric and magnetic forces. Students study data from charged objects, magnets, electromagnets, motors and generators, and ask testable questions about charge, distance, turns of wire and magnet strength. It is usually taught in grade 7 or 8 physical science.
Ask questions about data to determine the factors that affect the strength of electric and magnetic forces.
Clarification Statement: Examples of devices that use electric and magnetic forces could include electromagnets, electric motors, or generators. Examples of data could include the effect of the number of turns of wire on the strength of an electromagnet, or the effect of increasing the number or strength of magnets on the speed of an electric motor.
Assessment Boundary: Assessment about questions that require quantitative answers is limited to proportional reasoning and algebraic thinking.
Next Generation Science Standards · Disciplinary Core Idea: Motion and Stability: Forces and Interactions · Official standard
Students look at data about electric and magnetic forces and ask questions that find out what makes those forces stronger or weaker. For electric forces, the factors are the amount of charge on each object and the distance between them. For magnetic forces, they are the strength and number of magnets and the distance; for an electromagnet, they are also the number of turns of wire, the current and the material inside the coil. Students meet three devices that use these forces: electromagnets, electric motors and generators. Asking questions is the main practice: students sort testable questions from questions that cannot be tested, link each question to one variable, and use data to decide which question to ask next.
The NGSS Clarification Statement says: "Examples of devices that use electric and magnetic forces could include electromagnets, electric motors, or generators. Examples of data could include the effect of the number of turns of wire on the strength of an electromagnet, or the effect of increasing the number or strength of magnets on the speed of an electric motor." The Assessment Boundary says: "Assessment about questions that require quantitative answers is limited to proportional reasoning and algebraic thinking." Every calculation on this page uses ratios, rates or a simple pattern. All data sets are invented for teaching and labeled that way.
Learning Objectives
By the end of this lesson, students will be able to:
Ask testable questions about data that link one factor to the strength of an electric or magnetic force
Use data to describe how the amount of charge and the distance affect the strength of an electric force
Use data to describe how magnet strength, number of magnets, distance, turns of wire, current and core material affect a magnetic force
Explain how electromagnets, electric motors and generators use magnetic forces, and ask questions about data from each
Decide whether a data set shows a proportional pattern, and use proportional reasoning to make and question a prediction
Prior Knowledge Required
Students should already be comfortable with:
Electric and magnetic forces act between objects that are not touching 3-PS2-3
Magnets have north and south poles; like poles push apart and opposite poles pull together
Building a simple circuit with a battery, wire and switch
Recognizing proportional relationships in tables and graphs 7.RP.A.2
Show a fridge magnet holding one sheet of paper to a steel whiteboard, then try it with eight sheets: it slides down. Then pull a fleece jacket off a chair on a dry day and let students hear the crackle.
Warm-Up Prompt
"Write three questions about what makes a magnetic force or an electric force stronger or weaker. Then put a star next to any question you could answer with a test in this room."
Collect questions on sticky notes and sort them on the board into "we could test this" and "we can't test this here." Many students write "why" questions ("Why are magnets magnetic?"); keep them, and show how to turn one into a testable question: "Does the number of paper sheets change how strongly the magnet holds?"
Direct Instruction15-20 minutes
Electric forces. Objects can carry electric charge, positive or negative. Rubbing two materials together moves tiny charged particles from one to the other, so both become charged. Like charges push apart and opposite charges pull together. The electric force is stronger when the objects carry more charge and when they are closer together.
Magnetic forces. A magnet pulls on steel and pushes or pulls other magnets. The magnetic force is stronger with a stronger magnet or more magnets, and when the objects are closer. An electric current is a flow of charge, such as the flow from a battery through a wire. A current in a coil of wire makes a magnet called an electromagnet. Each loop of wire is one turn. More turns, more current (for example two D cells instead of one) and a steel core inside the coil all make it stronger.
Devices. An electric motor uses magnetic forces between a magnet and a current-carrying coil to make the coil spin. A generator does the reverse: spinning a coil and a magnet past each other makes magnetic forces push charges along the wire, which makes a current.
Asking questions about data. A testable question names one factor you change (the independent variable) and one result you measure (the dependent variable), for example "Does the number of turns change the mass an electromagnet lifts?" Good data answer one question and raise the next one.
Electric force and amount of charge
Invented data: a foam plate sits on a jeweler's scale. A PVC pipe rubbed with fleece is held 2.0 cm above it, and the plate is pulled up, so the scale reading drops. After 10 rubs the reading drops by 0.21 g; after 20 rubs, by 0.42 g.
Result: Twice the rubbing gave twice the drop, so more charge gave a stronger electric force. Next question: does the force keep growing if we rub 40 or 80 times?
Electric force and distance
Invented data: the same pipe, rubbed 20 times each trial, is held 1, 2, 3 and 4 cm above the plate. The scale reading drops by 1.60, 0.42, 0.19 and 0.11 g.
Result: Closer gives a stronger force, but the pattern is not proportional: from 2 cm to 1 cm the drop grew almost 4 times (1.60 ÷ 0.42 ≈ 3.8). Next question: is the pattern the same with a different pair of objects? Diagram 2 shows these data.
Electromagnet and number of turns
Invented data: enamel-coated wire is wound on a steel bolt with 25, 50, 75 and 100 turns, always connected to one D cell. The electromagnet lifts 8, 15, 24 and 31 g of steel nuts.
Result: The mass lifted is close to proportional to the turns: about 0.31 g per turn (Diagram 1). Next question: does the pattern continue past 100 turns, or does it level off?
Motor speed and number of magnets
Invented data: a simple coil motor (a wire coil resting on two supports above a magnet, powered by one D cell) spins at 300, 520 and 690 turns per minute (rpm) with 1, 2 and 3 ceramic magnets stacked under the coil.
Result: More magnets made the motor faster, but each extra magnet added less (220 rpm, then 170 rpm). Stacking magnets also moved the top magnet closer to the coil. Next question: was the change caused by the number of magnets or by the smaller gap?
A generator
Invented data: a hand crank spins a magnet next to a coil connected to a meter. At 1, 2 and 3 turns per second, the meter reads 0.12, 0.25 and 0.36 volts (V).
Result: Faster turning gave a larger voltage, close to proportional (about 0.12 V per turn per second). Next question: at the same speed, would a stronger magnet give a larger voltage?
After each example, ask: "Which factor changed? What was measured? Is the pattern proportional? What question should we ask next, and what data would answer it?"
Guided Practice15 minutes
Pairs study invented data for ceramic disc magnets stacked on a steel plate. A spring scale pulls the stack straight off the plate, and the reading just before it lets go is the pull-off force. In the second column, 10 sheets of paper (about 1 mm) sit between the stack and the plate.
Guided practice data (invented): pull-off force of stacked ceramic magnets
Number of magnets
No paper (N)
10 sheets of paper (N)
1
2.0
1.0
2
3.6
1.9
3
4.8
2.6
4
5.5
3.0
Name the two factors that change in this table. Which column or row shows each one?
With no paper, does doubling the number of magnets from 1 to 2 double the force? From 2 to 4? Is the pattern proportional?
Write two testable questions these data answer, and one testable question they cannot answer.
Write one question you would ask next, and say what you would change and measure to answer it.
Independent Practice10-15 minutes
Each student works with invented data from a homemade electroscope: a jar with two thin strips of aluminum foil hanging from a wire in the lid. A charged object touched to the wire charges both strips the same way, so they push apart. A PVC pipe is rubbed with fleece and touched to the wire, and students measure how far apart the strip ends spread.
Independent practice data (invented): electroscope strips
Rubs of the pipe
0
5
10
20
40
Spread of the strips (mm)
0
9
16
25
28
Students (1) describe how the spread changes with the number of rubs, (2) decide whether the pattern stays proportional, (3) write one question the data answer, one testable question to ask next and one question about why the spread levels off, and (4) name one factor other than rubbing that might change the electric force between the strips.
Closure5 minutes
Exit ticket: "A different electromagnet with 60 turns lifts 18 g of nuts. If the pattern is proportional, what should 120 turns lift? Write one question you would ask before trusting that prediction." (36 g; for example, "Does the battery run down during the test?" or "Does the pattern level off above 100 turns?") Return to the warm-up questions and move any that can now be tested.
Differentiation Strategies
For Struggling Students
Give a question frame: "Does changing the ___ change the ___?" and have students fill it in from a data table's column headings
Pre-label each data table with "what we changed" and "what we measured" before students write questions
Use the electromagnet lab first, where the result (nuts lifted) can be counted, before the electric force data in grams
For Advanced Students
Ask students to find the confounding variable in the motor data (the gap between the coil and the top magnet) and plan a test that removes it
Have students graph the electric force data against 1 ÷ distance and against 1 ÷ distance², and ask which graph looks most like a straight line (an extension beyond this standard; it is not assessed on this page)
Ask students to compare two magnet strengths fairly: what must be the same, besides the gap, for the comparison to count?
Assessment Guidance
What to Look For
Check that students' questions name one factor and one measured result, and that they can say which variable a data table changes. Look for students who call any increasing pattern "proportional" without checking ratios, and for students who treat a confounded result (two things changed) as proof of one cause. Listen for correct links between devices and forces: a motor uses magnetic forces to make motion, and a generator uses motion and magnetic forces to make current.
02
Classroom Activities
3 Activities
1
Build an Electromagnet: Turns, Cells and Cores
30 minGroups of 3
Groups wind enamel-coated wire around a core, connect it to D cells through a push-button switch, and count how many 2 g steel nuts it lifts. Each group tests one factor and collects data for the class table, then writes questions about the combined data.
Procedure
Turns groups: wind 30 turns on a steel bolt, test, then add turns to 60 and 90. Use one D cell.
Cells groups: 60 turns on a steel bolt, first one D cell, then two D cells in a holder.
Core groups: 60 turns and one D cell, wound on a steel bolt, an aluminum rod and a wooden dowel of the same size.
For each trial, press the button, touch the core to a pile of nuts, lift, and count the nuts that stay on. Run three trials and record the middle value (the median).
Safety: press the button for no more than 10 s at a time and let the wire cool between trials, because the wire and cells get warm. Use only alkaline D cells, never more than two, and never connect the wire to a wall outlet.
Is the number of nuts close to proportional to the number of turns? Use ratios to decide.
The aluminum rod and the wooden dowel lifted no nuts. What question does that raise about core materials?
Write one testable question that combines this class table with a new factor, such as wire thickness.
Modification for Distance Learning
Students analyze the sample data above and a short teacher video of each test, then post three questions: one the data answer, one testable next and one that cannot be tested with these materials.
2
Simple Coil Motor: Magnets and Speed
30 minGroups of 3
Groups build a simple coil motor: a coil of enamel-coated wire rests on two bent-wire supports connected to a D cell, with magnets underneath. They measure its speed from slow-motion video and test the official example: how the number and strength of magnets affect the speed. This time they keep the gap between the coil and the top magnet the same.
Procedure
Wind a coil of about 10 turns, leave two straight ends, and sand the coating off one end fully and off only the top half of the other end.
Rest the coil on the supports over one ceramic magnet and give it a gentle spin. Film it in slow motion for 2 s and count the turns; turns in 2 s × 30 = rpm.
Add a second and third magnet under the first, and lower the magnets on a stack of cards each time so the gap to the coil stays 1 cm. Then test one neodymium magnet at the same gap.
Safety: the coil and cell get hot, so disconnect after 20 s. Neodymium magnets snap together hard and can pinch: keep them apart, away from phones and out of mouths.
Compare these results with the worked example, where the gap was not controlled. Why might adding magnets raise the speed less here?
The neodymium magnet beat all three ceramic magnets together. What question does that raise about "number" versus "strength" of magnets?
Write a testable question about another factor that could change the motor's speed.
Challenge Variation
Groups predict, then test, how the speed changes when the gap is 2 cm instead of 1 cm with one ceramic magnet, and explain the result in terms of the strength of the magnetic force.
3
Question Storm: Data Card Sort
20 minPairs
Pairs get six data cards (all invented). For each card they name the factor that changed and the result that was measured, write two questions, and sort every question into "answered by these data," "testable next" or "not testable."
Data Cards
Card 1, bicycle dynamo (a small generator): wheel speed 2, 4 and 6 m/s; lamp voltage 1.1, 2.2 and 3.2 V.
Card 2, charged comb: a plastic comb run through dry hair 5, 10 and 15 times picks up 3, 7 and 10 puffed rice bits from 2 cm away.
Card 3, magnet and cardboard: 0, 2, 4 and 6 sheets of cardboard between a magnet and a steel plate; nuts held under the plate: 12, 7, 4 and 2.
Card 4, electromagnet cores: 60 turns, one D cell; steel bolt 14 nuts, brass bolt 0 nuts, aluminum rod 0 nuts.
Card 5, dry and humid days: the same electroscope test gives a 22 mm spread on a dry day and a 6 mm spread on a humid day.
Card 6, motor and battery: the same coil motor spins at 450 rpm with a fresh D cell and 190 rpm with a used one.
Discussion Questions
On which cards does the force or its effect grow as the factor increases? On which does it shrink?
Which card shows a factor that might change how much charge builds up, rather than the force itself?
Card 6 suggests a question about current. What would you measure to answer it?
Modification for Distance Learning
Post the cards on a shared board. Pairs add their questions as sticky notes in three colors, one for each category, and vote on the best "testable next" question for each card.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: Turns of Wire and Electromagnet Strength
Invented data from the third worked example, drawn to scale. The points lie close to a straight line through the origin, so the mass lifted is close to proportional to the number of turns, about 0.31 g per turn. The data cannot say what happens beyond 100 turns.
Diagram 2: Electric Force and Distance
Invented data from the second worked example, drawn to scale. The drop in the scale reading measures the electric pull on the foam plate. The force grows quickly as the pipe gets closer, so the pattern is not proportional and the points do not lie on a straight line.
04
Homework Assignment
~30 min
MS-PS2-3 Homework: Asking Questions About Force Data
Directions: All data are invented for practice. For each problem, name the factor that changed and the result that was measured, show any ratios you use, and write your questions as full sentences that could be tested.
Part 1: Electric Forces (Problems 1-2)
A foam cup sits on a jeweler's scale. A plastic ruler rubbed with fleece is held 3.0 cm above it. The drop in the scale reading after 4, 8, 12 and 16 rubs is 0.06, 0.12, 0.17 and 0.24 g. (a) Describe the pattern. (b) Is it close to proportional? Show two ratios. (c) Predict the drop after 20 rubs if the pattern continues. (d) Write one testable question about a factor other than rubbing.
Two foam cups are each rubbed with fleece, so they carry the same kind of charge. One sits on a jeweler's scale and the other is held above it. At 1.5, 3.0 and 6.0 cm apart, the scale reading rises by 0.80, 0.21 and 0.05 g. (a) Does the held cup push or pull on the cup on the scale? How do the data show it? (b) What happens to the force each time the distance doubles? (c) Is the force proportional to the distance? Explain. (d) Write a question about what would change if one cup were rubbed with a different material.
Part 2: Magnets, Electromagnets and Motors (Problems 3-4)
A model crane uses an electromagnet on a steel bolt. With one D cell, 40, 80, 120 and 160 turns lift 10, 21, 30 and 41 g. With two D cells, 80 turns lift 40 g. (a) Describe how the number of turns affects the mass lifted, and give the rate in grams per turn. (b) Predict the mass lifted by 200 turns with one cell. (c) Compare one cell and two cells at 80 turns. (d) Name two variables that stayed the same in the turns test. (e) Write one testable question about the core.
Another class builds a simple coil motor and keeps the gap between the coil and the top magnet at 1 cm. With 1, 2, 3 and 4 ceramic magnets the motor spins at 250, 370, 440 and 470 rpm. One neodymium magnet gives 600 rpm. (a) Find how much speed each extra ceramic magnet adds. Does it add the same amount each time? (b) Write a question about why the increase gets smaller. (c) Predict whether a fifth ceramic magnet would add more or less than 30 rpm, and explain. (d) To compare one neodymium magnet with one ceramic magnet fairly, what must stay the same?
Part 3: Generators and Good Questions (Problems 5-6)
A model wind turbine has magnets in its spinning part (the rotor) and a coil next to it. Invented data for the voltage: with 2 magnets, 2, 4 and 6 turns per second give 0.4, 0.8 and 1.2 V; with 4 magnets, the same speeds give 0.8, 1.6 and 2.4 V. (a) Name the two factors that change. (b) Is the voltage proportional to the turning speed? Show it. (c) What happens to the voltage when the number of magnets doubles? (d) Predict the voltage with 4 magnets at 5 turns per second. (e) Write one new testable question.
Sort these student questions into "testable" and "not testable," then rewrite two of the untestable ones so they can be tested: (1) "Are magnets cool?" (2) "Does the number of D cells change how many nuts an electromagnet lifts?" (3) "Why do magnets exist?" (4) "How does the distance between a charged comb and paper bits change how many bits it picks up?" (5) "Is a bigger magnet always better?" (6) "Which is stronger, electricity or magnetism?" Then pick one testable question and describe the data table you would use to answer it.
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
Reading the Data
Factor and measured result named; pattern described with numbers from the data
Pattern described in words only, or the factor misnamed
Proportional Reasoning
Ratios or rates shown; proportional or not correctly decided; predictions correct
Correct method with one calculation error
Asking Questions
Questions name one factor and one measured result and could be tested with real materials
Questions are on topic but name two factors at once or no measurement
05
Quiz: 20 Questions
Interactive, with answers
Instructions
All data are invented. Your score updates as you answer, and Reset quiz clears everything so you or your students can try again.
Multiple choice: pick an option to check it. Short answer: write your answer, then reveal the model answer.
0 of 20 answered · 0 correct
Question 1 of 20 · Multiple Choice
Which change makes the electric force between two charged objects stronger?
Answer: D
More charge on the objects gives a stronger electric force. Choice A weakens the force, because electric forces get weaker with distance. Choice B confuses mass with charge. Choice C usually weakens the force, because charge slowly leaks away into the air.
Question 2 of 20 · Multiple Choice
An electromagnet with 30 turns lifts 6 nuts. If the pattern is proportional, how many nuts should 90 turns lift?
Answer: A
90 turns is 3 times 30 turns, so a proportional pattern gives 3 × 6 = 18 nuts. Choice B only doubles. Choice C adds the 60 extra turns to the 6 nuts. Choice D divides 90 by 6.
Question 3 of 20 · Multiple Choice
A class has steel bolts, wire, D cells and steel nuts. Which question can it test?
Answer: C
Choice C names one factor to change (turns) and one result to measure (nuts lifted), and the class has the materials. Choice A is a "why" question these materials cannot answer. Choice B does not say what "better" means or what to measure. Choice D is a history question.
Question 4 of 20 · Multiple Choice
Invented data: a charged pipe held 1, 2 and 3 cm above a foam plate makes a scale reading drop by 1.20, 0.30 and 0.13 g. Which statement do the data support?
Answer: B
The drop gets smaller as the pipe moves away, so the force weakens with distance. Choice A is wrong: a proportional pattern would grow with distance, and doubling the distance here cut the drop to one quarter. Choices C and D contradict the data.
Question 5 of 20 · Multiple Choice
A group tests an electromagnet with one D cell and 50 turns, then with two D cells and 100 turns. It lifts 15 g, then 58 g. Which question can the data NOT answer?
Answer: D
Two factors changed at once, so the data cannot show which one caused the increase. Choices A, B and C ask about results the group measured directly, so the data do answer them.
Question 6 of 20 · Multiple Choice
In a model generator, a hand crank spins a magnet next to a coil. Which change would make the voltage larger?
Answer: C
Moving the magnet past the coil faster makes the magnetic forces on the charges in the wire act more strongly, so the voltage rises. Choices A, B and D each weaken the effect: slower motion, a weaker magnet and fewer turns all lower the voltage.
Question 7 of 20 · Multiple Choice
A rubbed PVC pipe pushes a rubbed foam cup away. What can you conclude?
Answer: A
Like charges push apart, so the pipe and the cup carry the same kind of charge. Choice B describes a pull, not a push. Choice C is wrong because a charged object attracts an uncharged one; it does not push it away. Choice D is wrong because neither object is a magnet.
Question 8 of 20 · Multiple Choice
Two electromagnets each have 60 turns on the same steel bolt and one D cell. The one wound with thin wire lifts 6 nuts; the one wound with thicker wire lifts 11 nuts. Which factor do these data test?
Answer: B
Only the wire's thickness changed: the turns, the bolt and the cell stayed the same. Thicker wire lets more current flow, which makes the electromagnet stronger. Choices C and D name factors that were kept the same, and choice A was not changed on purpose or measured.
Question 9 of 20 · Multiple Choice
Invented data: the pull-off force of 1, 2 and 3 stacked ceramic magnets is 2.4, 4.1 and 5.2 N. Which statement fits the data?
Answer: D
The force rises by 1.7 N, then by 1.1 N, so each added magnet adds less. Choices A and C would need equal steps (proportional would give 4.8 and 7.2 N). Choice B contradicts the data.
Question 10 of 20 · Multiple Choice
On humid days, a rubbed comb picks up fewer paper bits than on dry days. Which is a testable question about this?
Answer: C
Choice C names one factor (humidity, which can be measured) and one result (how many bits the comb picks up). Choice A is about weather, not electric force. Choice B is not defined well enough to measure, and choice D is an opinion survey.
Question 11 of 20 · Multiple Choice
A student tests whether the number of turns affects an electromagnet. Which variable must stay the same?
Answer: A
The number of cells sets the current, which also changes the strength, so it must be kept the same. Choice B is the factor being tested, and choices C and D are results being measured.
Question 12 of 20 · Multiple Choice
A bicycle dynamo (a small generator) gives 1.5 V at a wheel speed of 3 m/s. If the voltage is proportional to the speed, what voltage should it give at 5 m/s?
Answer: B
The rate is 1.5 ÷ 3 = 0.5 V per m/s, so at 5 m/s the voltage is 5 × 0.5 = 2.5 V. Choice A adds the 2 m/s of extra speed to 1.5 V. Choice C flips the ratio (1.5 × 3 ÷ 5). Choice D multiplies 1.5 by 5.
Question 13 of 20 · Multiple Choice
Invented data: at 4 cm, a charged pipe makes a scale reading drop by 0.05 g; at 2 cm, by 0.20 g. If the same pattern holds when the distance is halved again, what drop should you expect at 1 cm?
Answer: C
Halving the distance from 4 cm to 2 cm multiplied the drop by 4 (0.20 ÷ 0.05 = 4), so halving it again gives 4 × 0.20 = 0.80 g. Choice A only doubles. Choice B adds the same 0.15 g step again. Choice D halves the drop, as if closer meant weaker.
Question 14 of 20 · Multiple Choice
Which device uses an electric current and magnetic forces to make something spin?
Answer: D
An electric motor uses magnetic forces between a magnet and a current-carrying coil to make the coil spin. Choice A is the reverse: a generator uses spinning to make a current. Choices B and C do not use magnetic forces to make motion.
Question 15 of 20 · Short Answer
Invented data: an electromagnet with 20, 40, 60 and 80 turns lifts 5, 11, 15 and 21 g. (a) Describe the pattern. (b) Predict the mass for 120 turns. (c) Write one question you would ask before trusting the prediction.
(a) More turns lift more mass, close to proportional: about 0.26 g per turn (21 ÷ 80). (b) 120 × 0.26 ≈ 31 g (any answer from 30 to 32 g with the reasoning shown). (c) For example: "Does the pattern keep going past 80 turns, or does it level off?" or "Does the cell run down as the coil gets longer?"
Question 16 of 20 · Short Answer
Write two testable questions about factors that could change the electric force between a charged comb and bits of paper. For each, name what you would change and what you would measure.
Sample answers: (1) "Does the number of times I run the comb through my hair change how many bits it picks up?" Change: number of strokes. Measure: bits picked up. (2) "Does the distance between the comb and the paper change how many bits jump up?" Change: distance in cm. Measure: bits picked up. Each question changes one factor and keeps the others the same.
Question 17 of 20 · Short Answer
Invented data: a coil motor spins at 480 rpm with the magnet 1 cm below the coil, 300 rpm at 2 cm and 160 rpm at 3 cm. Which factor changed, what happened to the speed, and what does this suggest about the magnetic force?
The distance between the magnet and the coil changed. The speed dropped as the gap grew (480, then 300, then 160 rpm). This suggests the magnetic force on the coil gets weaker with distance, so the coil is pushed less hard each turn.
Question 18 of 20 · Short Answer
A student says, "Turning a generator faster makes its magnet stronger, and that is why the voltage goes up." Respond using the factors from this lesson.
The magnet's strength does not change with speed; the same magnet is used at every speed. What changes is how fast the magnet and coil move past each other. Faster motion makes the magnetic forces on the charges in the wire act more strongly, so the voltage rises. A stronger magnet would be a separate factor to test at the same speed.
Question 19 of 20 · Short Answer
Invented data: a pipe rubbed 10 times makes a scale reading drop by 0.6 g. If the drop is proportional to the number of rubs, how many rubs would give a drop of 1.5 g? Then write one question about whether the pattern really continues.
The rate is 0.6 ÷ 10 = 0.06 g per rub, so 1.5 ÷ 0.06 = 25 rubs. Question, for example: "Does the drop keep growing at the same rate after 20 rubs, or does the pipe stop picking up more charge?"
Question 20 of 20 · Short Answer
A student asks, "Do magnets work better?" Rewrite this as a testable question about the strength of a magnetic force, and describe the data you would collect.
Sample: "Does the number of sheets of paper between a magnet and a steel plate change the force needed to pull the magnet off?" Data: a table with the number of sheets (0, 5, 10, 15, 20) and the pull-off force in newtons from a spring scale, with three trials for each and the same magnet and plate every time.
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does MS-PS2-3 mean?
MS-PS2-3 asks middle school students to ask questions about data to find out what affects the strength of electric and magnetic forces. Students look at data from charged objects, magnets and devices such as electromagnets and motors, and ask questions that link one factor to the strength of the force. The code means Middle School, Physical Science, core idea 2 (Motion and Stability: Forces and Interactions), performance expectation 3.
What grade is MS-PS2-3 for?
It is a grades 6-8 standard, and schools place it in different years. Many teach it in grade 7 or grade 8 physical science, close to MS-PS2-5 on fields. The math is ratios, rates and simple patterns.
What is the assessment boundary for MS-PS2-3?
The official Assessment Boundary says that questions needing number answers are limited to proportional reasoning and algebraic thinking. Students can use rates such as grams per turn and spot patterns in tables, but formulas such as Coulomb's law are beyond this standard; they come in high school, in HS-PS2-4.
What factors affect the strength of an electric force?
The amount of charge on each object and the distance between them. More charge gives a stronger force, and the force gets weaker quickly as the objects move apart. Whether the force pushes or pulls depends on the kinds of charge: like charges push apart and opposite charges pull together.
What factors make an electromagnet stronger?
More turns of wire, more current and a steel or iron core inside the coil. Distance also matters: an electromagnet pulls hardest on objects close to its end. Students can test each factor with a bolt, wire, D cells and small steel nuts, changing one factor at a time.
What is a testable question in science?
A testable question can be answered by changing one thing and measuring a result. "Does the number of turns change the mass an electromagnet lifts?" is testable; "Why do magnets exist?" is not testable in a classroom. Testable questions usually name the factor (independent variable) and the measured result (dependent variable).
How do motors and generators use magnetic forces?
In a motor, a current in a coil makes it a magnet, and the push and pull between the coil and a fixed magnet makes the coil spin. In a generator, spinning a coil and a magnet past each other pushes charges along the wire, which makes a current. Both depend on the same factors: magnet strength, number of turns and distance.
Is it safe to build electromagnets in middle school?
Yes, with simple rules. Use alkaline D cells, never more than two, and never a wall outlet. Press the switch for only a few seconds at a time, because the wire and the cells get warm. Keep strong neodymium magnets apart, since they can pinch fingers.
Why do some data sets level off instead of staying proportional?
Real devices have limits. A steel core can only become so magnetized, a battery can only push so much current, and a rubbed object can only hold so much charge before it leaks into the air. When data level off, a good next question asks what limit was reached.
How does MS-PS2-3 connect to high school physics?
It prepares students for HS-PS2-4, where they use Coulomb's law to calculate electric forces, and HS-PS2-5, where they investigate how a current makes a magnetic field and a changing magnetic field makes a current. In middle school, MS-PS2-5 adds evidence that fields exist between objects that are not touching.
07
Related Standards
5 standards
These standards connect to MS-PS2-3: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
3-PS2-3Prerequisite
Ask questions about cause and effect in electric or magnetic interactions
Lesson coming soon
Alongside
MS-PS2-5Parallel
Investigate evidence that fields exist between objects that are not touching
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