HS-PS2-5: Investigating Electromagnetism and Induction
In plain English: HS-PS2-5 is the NGSS high school performance expectation that asks students to plan and conduct investigations showing that an electric current produces a magnetic field and that a changing magnetic field produces an electric current. Students gather evidence with compasses, coils, magnets and meters. It is usually taught in Physics or Physical Science.
Plan and conduct an investigation to provide evidence that an electric current can produce a magnetic field and that a changing magnetic field can produce an electric current.
Assessment Boundary: Assessment is limited to designing and conducting investigations with provided materials and tools.
Next Generation Science Standards · Disciplinary Core Idea: Motion and Stability: Forces and Interactions · Official standard
Students plan and carry out investigations that give evidence for two claims: an electric current produces a magnetic field, and a changing magnetic field produces an electric current. For the first claim they watch a compass near a wire or coil as they switch the current on, change its size and reverse it, and they count the paper clips an electromagnet lifts. For the second they push, pull and hold magnets in coils connected to a sensitive meter, and they switch a current on and off in a nearby coil. Each investigation needs a testable question, clear variables, a control trial, repeated trials and a claim backed by the data.
HS-PS2-5 has no Clarification Statement. The Assessment Boundary says: "Assessment is limited to designing and conducting investigations with provided materials and tools." So every plan on this page uses a listed set of classroom equipment, and students are not asked to use formulas for field strength or induced voltage. Those formulas are beyond this standard; teachers used them only to make sure the invented data sets are physically realistic. All data on the page are invented for teaching and match what classroom equipment typically shows.
Learning Objectives
By the end of this lesson, students will be able to:
Plan an investigation with provided materials, naming the independent, dependent and controlled variables, a control trial and the number of repeated trials
Conduct an investigation safely and record compass deflections, paper clip counts or meter readings in a data table
Use data (a needle that moves only when current flows, and reverses when the current reverses) as evidence that an electric current produces a magnetic field
Use data (a meter that reads only while a magnet or a nearby current is changing) as evidence that a changing magnetic field produces an electric current
Critique an investigation plan and revise it so that only one variable changes at a time
Prior Knowledge Required
Students should already be comfortable with:
Magnets have north and south poles, and like poles repel MS-PS2-3
Fields exist between objects that exert forces on each other without touching MS-PS2-5
A current flows only in a complete circuit, and an ammeter measures it
Finding the mean of repeated trials and spotting an outlier
Lay a long insulated wire along the table in a north-south line and set a compass directly under it. Connect it to the power supply through an open switch. Before closing the switch, ask:
Warm-Up Prompt
"When I close this switch, the compass needle swings. When I open it, the needle swings back. What claim could this observation support? Before you believe that claim, what else would you want to test, and what result would change your mind?"
Collect ideas on the board. Students often suggest reversing the battery, moving the compass farther away, or checking whether the wire itself is magnetic. Keep the list: these are the controls and variables of the investigations that follow.
Direct Instruction15-20 minutes
What counts as evidence. A claim about cause needs a test in which only one thing changes. For the claim that a current produces a magnetic field, the independent variable is the current (on or off, its size, its direction) and the dependent variable is a magnetic effect, such as the deflection of a compass or the number of paper clips lifted. For the claim that a changing magnetic field produces a current, the independent variable is how the field inside a coil changes (in, out, still, fast, slow) and the dependent variable is the meter reading. A control trial keeps everything the same except the suspected cause, for example the switch left open or the magnet held still. Repeated trials show how much the readings vary by chance. Use Diagram 1 with Example 1 and Diagram 2 with Example 3.
Current and a compass (invented data)
A wire runs north-south 2.0 cm above a compass. With the switch open the needle points north (0°). The current is set to 0.5, 1.0 and 2.0 A, then reversed at the same three sizes.
Result: Deflection: 13°, 24° and 42° east for the forward current; 13°, 24° and 42° west for the reversed current. The needle moves only when current flows, turns farther for a larger current and turns the other way when the current reverses: evidence that the current produces a magnetic field.
Turns on an electromagnet (invented data)
An iron nail is wrapped with 10, 20, 30 and 40 turns of insulated wire. The current stays at 1.0 A. Each setting is tested three times, and the nail is checked before each trial to make sure it lifts no clips with the switch open.
Result: Mean clips lifted: 2.3, 5.0, 7.3 and 9.7. With the switch open: 0 clips every time. More turns carrying the same current give a stronger magnet, and no current gives no magnet.
A magnet and a coil (invented data)
A 200-turn coil is connected to a center-zero meter. A bar magnet's north pole is pushed in, held still inside for about a second, then pulled out. Next the north pole is pushed in about twice as fast, and finally the south pole is pushed in at the first speed.
Result: Peak readings: push in +180 µA; held still 0 µA; pull out -170 µA; faster push +350 µA; south pole in -180 µA. Current flows only while the field inside the coil is changing, its direction depends on how the field changes, and a faster change gives a larger current.
Turns on the pickup coil (invented data)
The same magnet is dropped from 20 cm through a cardboard tube wound with 100, 200, 300 and 400 turns. A voltage sensor records the peak voltage across the coil.
Result: Peak voltage: 21, 40, 62 and 81 mV, about 0.2 mV per turn every time. Dropping from the same height keeps the speed the same, so the number of turns is the only change.
Switching a current near a coil
Two coils are wound on one iron rod. Coil A connects to a battery through a switch; coil B connects only to a meter. Nothing moves.
Result: Closing the switch gives a brief kick on coil B's meter, the reading returns to zero while the switch stays closed, and opening the switch gives a kick the other way. The current in coil A makes a field (the first claim); only while that field is growing or shrinking does it produce a current in coil B (the second claim).
After each example, ask: "What changed, what was measured, and which trial is the control?" Point out that Example 5 changes the magnetic field without any motion, which rules out the idea that a moving magnet is needed.
Safety. Never connect a bare wire straight across a battery or power supply: with almost no resistance the current is large, and the wire and cell get hot. Use a supply with a current limit (or a series resistor), close the switch for no more than 10 seconds at a time, wear goggles, and never use wall-outlet power.
Guided Practice15 minutes
Pairs plan an investigation of this question using only a bar magnet, a 200-turn coil, a meter and a ruler: "Is it the motion of the magnet that matters, or the motion of the magnet and coil relative to each other?" They write the independent variable, the dependent variable, two controlled variables and a control trial. Then show the class results below (invented) and have pairs compute each mean.
Guided practice data: peak meter reading (µA), three trials each
Trial type
Trial 1
Trial 2
Trial 3
Magnet pushed into a fixed coil
95
102
98
Coil pushed over a fixed magnet, same speed
97
94
100
Magnet taped inside coil, both moved together
0
0
0
Magnet and coil both at rest
0
0
0
Find the mean of each row. The first two means are 98.3 µA and 97.0 µA.
Compare the difference between those two means (1.3 µA) with the spread within each row (7 µA and 6 µA). Is the difference larger than the chance variation?
Explain what the third row adds: the magnet moves, but the field inside the coil does not change.
Write a claim with evidence: the current depends on a change in the field inside the coil, which comes from relative motion, not from motion alone.
Independent Practice15 minutes
Part A, critique a plan. A student wants to test whether more turns make a stronger electromagnet. The plan: "Wrap nail A with 10 turns and connect it to a new D cell. Wrap nail B with 40 turns and connect it to an old D cell from the drawer. Count the paper clips each nail lifts once." Students list at least three problems and rewrite the plan with provided materials.
Part B, analyze data. A flat coil of radius 5 cm stands on edge in a north-south plane with a compass at its center. The current is fixed at 0.20 A while the number of turns changes (invented data):
Independent practice data: compass at the center of a flat coil, 0.20 A
Turns
Switch open
5
10
15
20
Deflection (degrees)
0
30
49
60
66
Students describe the trend, decide whether doubling the turns doubles the deflection angle, and write a claim, evidence and reasoning paragraph for the claim that the current in the coil produces the magnetic field. Advanced students can compare the tangent of each angle (0.58, 1.15, 1.73, 2.25), which rises in step with the number of turns because the compass responds to the coil's field and Earth's field together.
Closure5 minutes
Exit ticket: "Name one observation from today that shows a current produces a magnetic field, and one that shows a changing magnetic field produces a current. For the second, name the control trial that shows the magnet's field alone, without a change, is not enough." Return to the warm-up list and check off each test the class carried out.
Differentiation Strategies
For Struggling Students
Give a planning frame with blanks: "I will change ___. I will measure ___. I will keep ___ and ___ the same. My control trial is ___."
Start with the yes-or-no version of each test (switch open or closed, magnet moving or still) before asking about size or direction
Provide a data table with the columns already labeled and a row for the mean
For Advanced Students
Ask students to predict and then test how the compass deflection changes when the compass is placed above the wire instead of below it, and to sketch the field lines that explain it
Have students compare the tangents of the compass angles in the independent practice data and explain why the angle itself is not proportional to the number of turns
Ask students to design a single investigation, with provided materials, that gives evidence for both claims at once
Assessment Guidance
What to Look For
Check that each plan changes one variable, names what stays the same and includes a control trial with the current off or the magnet still. Look for data tables with repeated trials and a mean. Listen for students who say a magnet near a coil always makes a current: the evidence says only a changing field does. Watch for unsafe circuits with no current limit.
02
Classroom Activities
3 Activities
1
Build and Test an Electromagnet
25 minGroups of 3-4
Groups plan and conduct an investigation of how the current in a coil affects the strength of an electromagnet. They wind 30 turns of insulated wire on an iron nail, set the current with the power supply, and count the steel paper clips the nail lifts from a pile.
Procedure
Before winding, touch the bare nail to the clips. If it lifts any, swap it for a fresh nail so that leftover magnetism does not affect the results.
Wind 30 turns, leave 20 cm of wire at each end, and connect the coil to the supply through a switch and an ammeter.
Set the current to 0.5 A, close the switch, lower the nail into the clips, lift it 5 cm and count. Open the switch. Do three trials, then repeat at 1.0 A and 1.5 A.
Control trials: the switch open, and the coil wound on a pencil (no iron) at 1.5 A.
Safety: goggles on; close the switch for no more than 10 seconds at a time, because the coil warms up; open the switch before touching bare wire ends.
The means are 3.3, 7.0 and 10.7 clips. The mean at 1.5 A is about three times the mean at 0.5 A. What does that suggest about how the strength depends on the current?
The pencil-core coil lifted no clips. Does that prove it had no magnetic field? How could you test it with a compass?
Why check the bare nail before winding it?
Modification for Distance Learning
Students use a free electromagnet simulation that shows a compass and field lines, or analyze the sample data above, then post their plan, table and claim to the class board.
2
Induction Stations: What Makes the Meter Move?
20 minPairs
Pairs rotate through four stations with a coil connected to a center-zero meter. At each station they predict the reading, test it three times, and record the peak reading and its sign. The goal is to find out which condition every nonzero reading has in common.
Stations
Station 1: push a bar magnet into the coil slowly (about 1 s), then quickly (about 0.2 s).
Station 2: leave the magnet resting inside the coil for 20 s.
Station 3: two coils on one iron rod; close the switch in the first coil, keep it closed, then open it, while watching the meter on the second coil.
Station 4: spin a magnet on a pencil near the end of the coil, about 2 turns per second.
Sample Data (invented)
Station 1: slow push +35 µA, quick push +160 µA. Station 2: 0 µA for the full 20 s. Station 3: switch closed +25 µA, held closed 0 µA, opened -28 µA. Station 4: the needle swings between about +20 and -20 µA, two full swings each second.
Discussion Questions
In which two cases did the meter read zero even though a magnetic field was inside the coil? What do they have in common?
The quick push gave between 4 and 5 times the reading of the slow push. What does that tell you?
At Station 4 the needle swings back and forth twice each second. Why does it change direction?
Challenge Variation
Pairs design, and then run, a test of whether an iron rod placed inside the coil changes the reading at Station 1, keeping the magnet and the push time the same.
3
Design Challenge: Plan from a Materials List
25 minGroups of 3-4
Each group draws a question card and gets a tray with a fixed materials list. They write a full plan, trade plans with another group for a peer review, revise, and then carry out their own plan.
Question Cards and Materials
Card A: Does an iron core make a coil's magnetic field stronger? (50-turn coil on a straw, iron rod, compass, ruler, power supply)
Card B: Does the direction of the current change the direction of the field? (wire, compass, power supply, switch)
Card C: Does the height a magnet falls from change the current it makes in a coil? (cardboard tube coil, magnet, meter, ruler, foam pad)
Card D: Can a changing current make a current in a coil that it never touches? (two coils, iron rod, switch, battery, meter)
Peer-review checklist: one independent variable; a measured dependent variable with units; at least two controlled variables; a control trial; three trials per setting; a safety step; a data table ready to fill in.
Sample Data for Card A (invented)
Coil at 1.0 A, compass 10 cm from one end, on the coil's axis. Air core: 2°, 3°, 2°. Iron rod core: 55°, 58°, 56°. Switch open, either core: 0°.
Discussion Questions
Card A: the mean deflection rose from about 2° to about 56°. Is the difference much larger than the spread of the trials?
Which card's plan was hardest to control, and why?
What did the peer reviewers catch that your group missed?
Modification for Distance Learning
Groups write the plan in a shared document, a reviewer from another group comments on it, and the teacher runs the revised plan on camera while groups record the data.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: Compass Deflection Against Current in a Wire
Example 1's invented data, drawn to scale. With the switch open the deflection is zero; forward currents of 0.5, 1.0 and 2.0 A turn the needle 13°, 24° and 42° one way, and the same currents reversed turn it the same amounts the other way. The mirror pattern is evidence that the current, not the wire itself, makes the field.
Diagram 2: Meter Reading While a Magnet Moves In, Stays and Moves Out
Example 3's invented meter trace for a 200-turn coil, drawn to scale. The reading spikes to +180 µA while the north pole is pushed in, falls to zero while the magnet is held still inside, and spikes to -170 µA while it is pulled out. Current flows only while the field inside the coil changes.
04
Homework Assignment
~30 min
HS-PS2-5 Homework: Planning and Analyzing Electromagnetism Investigations
Directions: All data are invented for practice. Use only the materials each problem lists. For every plan, name the independent variable, the dependent variable, at least two controlled variables and a control trial, and include one safety step. End each data problem with a claim that names your evidence.
Part 1: Planning Investigations (Problems 1-2)
You are given a power supply set to 2.0 A, a long straight wire, a switch, a compass, a ruler, and a sheet each of cardboard, glass and aluminum foil. Plan an investigation to test whether placing one of these materials between the wire and the compass changes the deflection. (a) Name the variables and a control trial. (b) Draw the data table you would fill in. (c) Describe the result that would show that these materials do not block the magnetic field.
A student plans to test whether moving a coil (instead of a magnet) can produce a current: "I will hold a strong magnet in one hand and move the coil past it with the other, as fast as I can, one time, and I will use a different magnet if the meter does not move." (a) Identify two problems with this plan. (b) Rewrite it so it gives clear evidence, using a bar magnet, a 200-turn coil, a meter, a ruler and a stopwatch.
Part 2: Analyzing Data (Problems 3-4)
A compass is placed below a north-south wire carrying 3.0 A, at distances of 1, 2, 3 and 4 cm. The deflections are 70°, 54°, 42° and 34°. With the switch open, the deflection is 0° at every distance. (a) Describe the pattern. (b) What does the switch-open trial rule out? (c) Predict whether the deflection at 6 cm will be larger or smaller than 34°, and explain.
The same magnet is dropped through a 150-turn coil from heights of 5, 20 and 45 cm. Its speed at the coil is about 1.0, 2.0 and 3.0 m/s, and the peak voltages are 15, 31 and 44 mV. A trial with the magnet resting in the coil reads 0 mV. (a) How does the peak voltage change when the speed triples? (b) Write a claim about what the size of the induced voltage depends on. (c) Why is dropping the magnet a better method than pushing it by hand?
Part 3: Explaining with Evidence (Problems 5-6)
A coil connected to a meter sits next to an electromagnet powered by a variable supply. A student turns the supply knob slowly from 0 to 2 A over 4 s: the meter shows a small steady reading of +12 µA. She holds the current at 2 A: the reading is 0. She turns it back down to 0 over 4 s: the reading is -12 µA. (a) Explain each reading. (b) Predict the reading if she turns the knob from 0 to 2 A in 2 s. (c) Which of the two claims of HS-PS2-5 does this investigation support, and how?
A classmate argues that the compass near a current-carrying wire moves because the wire gets warm, not because of magnetism. With 2.5 A, the needle turns 48° east; with the current reversed, it turns 47° west. The wire's temperature after 5 s is 24.3 °C and 24.4 °C in the two trials (room temperature 23.8 °C). Write a claim, evidence and reasoning response to the classmate.
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
Investigation Plan
One independent variable, a measured dependent variable, two or more controlled variables, a control trial, repeated trials and a safety step
Plan is testable but misses the control trial or changes more than one variable
Data Analysis
Correct pattern or means, with units, and the control trial used as evidence
Pattern described but control trial ignored or one calculation error
Claim, Evidence, Reasoning
Claim names specific readings and explains how they support the current-makes-field or changing-field-makes-current claim
Claim stated but evidence is general or reasoning is missing
05
Quiz: 20 Questions
Interactive, with answers
Instructions
All data are invented for practice, and every setup uses ordinary classroom equipment. 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
A compass under a wire points north with the switch open. It swings when the switch is closed and swings back when it is opened. Which claim does this evidence best support?
Answer: A
The needle responds only while current flows, so the current is linked to a magnetic effect. Choice B would make the needle move even with the switch open. Choice C describes the second claim of the standard, but here the current is the cause and the needle's motion is the effect. Choice D fails because the needle ignores the copper wire when no current flows.
Question 2 of 20 · Multiple Choice
A group tests whether more turns of wire make a stronger electromagnet. They keep the current at 1.2 A and count paper clips for 15, 30 and 45 turns. What is the independent variable?
Answer: C
The independent variable is the one the group changes on purpose: the number of turns. Choice A is the dependent variable (what they measure). Choices B and D are controlled variables that must stay the same.
Question 3 of 20 · Multiple Choice
A magnet dropped through a coil wound on a cardboard tube gives a 30 mV peak. Which trial is the best control to show that the voltage comes from the magnet's field and not from something falling through the tube?
Answer: D
A control trial keeps everything the same except the suspected cause. The steel rod falls the same way but has no magnetic field of its own, so a reading near zero shows the magnet's field is what matters. Choices A and B change the setting of the test instead of removing the suspected cause. Choice C gives no data at all.
Question 4 of 20 · Multiple Choice
A student turns a small coil by hand between the poles of a horseshoe magnet, and the meter swings back and forth. When she stops turning, with the coil still between the poles, the reading drops to zero. Which conclusion is best supported?
Answer: B
The field is still there when the coil stops, but it no longer changes through the coil, so the current stops. Choice A has no evidence: the magnet was not changed. Choice D contradicts the zero reading, which was taken in the same strong field.
Question 5 of 20 · Multiple Choice
A compass placed below a north-south wire turns east when the current flows south. The same compass is moved to just above the wire with the same current. What happens?
Answer: C
The field circles the wire, so above the wire it points the opposite way from below it, and the needle turns west. Choice A assumes the field points the same way everywhere. Choice D would need the field to be much stronger than Earth's field and pointing south, which neither position gives.
Question 6 of 20 · Multiple Choice
An electromagnet lifts 4, 5 and 3 clips at 0.6 A and 8, 9 and 7 clips at 1.2 A. Which statement is supported by the data?
Answer: A
The means are (4 + 5 + 3) ÷ 3 = 4 and (8 + 9 + 7) ÷ 3 = 8 clips, so doubling the current doubled the mean. Choice B reports the sums, not the means. Choice D confuses the spread of the trials with the result: equal ranges say the trials were equally consistent, not that the means were equal.
Question 7 of 20 · Multiple Choice
Pushing the south pole of a magnet into a coil gives a peak reading of -60 µA. What reading do you expect when the south pole is pulled back out at the same speed?
Answer: D
Pulling the pole out changes the field inside the coil in the opposite way from pushing it in, so the current reverses: about +60 µA. Choice A ignores the reversal. Choice B would only happen if the magnet stopped moving.
Question 8 of 20 · Multiple Choice
Which of these would NOT produce a current in a coil connected to a meter?
Answer: B
A still magnet makes a field that does not change, so no current flows. Choices A and C change the field through the coil by motion, and choice D changes it by turning on a nearby current, so all three produce a reading.
Question 9 of 20 · Multiple Choice
A different magnet is pushed 6 cm into a 100-turn coil, taking 0.30 s, 0.15 s and 0.10 s in three trials. The peak readings are 40, 80 and 120 µA. Which claim do the data best support?
Answer: C
The average speeds are 0.2, 0.4 and 0.6 m/s, and the readings rise in the same ratio (1 : 2 : 3), so a faster change gives a larger current. Choice A reverses the pattern: the longest push gave the smallest current. Choice D has no evidence, since the same magnet was used and speed alone explains the pattern.
Question 10 of 20 · Multiple Choice
A plan tests whether the push speed of a magnet affects the induced current. Which pair of variables must stay the same in every trial?
Answer: A
The magnet and the coil (its number of turns) both affect the current, so they must be controlled. The push speed is the independent variable and the meter reading is the dependent variable, so choices B, C and D each hold fixed something that must be changed or measured.
Question 11 of 20 · Multiple Choice
Three trials at the same setting give 7, 8 and 21 paper clips. What should the group do?
Answer: D
The 21 is far from the other two trials, so it is likely an error; the group should look for the cause and run the trial again before finding the mean. Choice A averages in the suspect value: (7 + 8 + 21) ÷ 3 = 12, well above the other two trials. Choice B picks one trial without reason.
Question 12 of 20 · Multiple Choice
Before closing the switch in the compass-and-wire test, the wire is laid along the compass needle, in a north-south line. Why?
Answer: B
Earth's field lines up the needle north-south. The wire's field circles the wire, so under a north-south wire it points east-west, across the needle, which gives a clear deflection from a known zero. Choice D is impossible: Earth's field is always present, which is why the switch-open reading is the reference.
Question 13 of 20 · Multiple Choice
A group tests the current at 0.5, 1.0 and 1.5 A, but between settings they also rewind the nail with more turns. What is wrong with their plan?
Answer: A
A fair test changes one independent variable at a time. Here both the current and the turns change, so a larger clip count could come from either. Choice D ignores this, and choice B would remove the independent variable altogether.
Question 14 of 20 · Multiple Choice
A weaker magnet is dropped from the same height through coils of 150 and 450 turns. The peak voltages are 12 mV and 37 mV. What do the data show?
Answer: D
450 ÷ 150 = 3, and 37 ÷ 12 ≈ 3.1, so tripling the turns about tripled the voltage. Choice B misreads the ratio. Dropping from the same height kept the speed the same, so the number of turns is the only change.
Question 15 of 20 · Short Answer
Plan an investigation, using a 40-turn coil on an iron nail, a power supply with a current limit and ammeter, a switch, a steel washer and a spring scale, to test whether the current affects the pull of the electromagnet. Name the independent variable, the dependent variable, two controlled variables and a control trial.
Independent variable: the current (for example 0.5, 1.0, 1.5 A). Dependent variable: the spring scale reading needed to pull the washer off the nail, in newtons. Controlled: the number of turns, the same nail and washer, and the direction of the pull. Control trial: the switch open, where the scale should read only the washer's weight. Do three trials per current and close the switch only for a few seconds.
Question 16 of 20 · Short Answer
A compass sits next to a coil. The deflection is 0° at 0 A, 25° at 0.3 A and 43° at 0.6 A; with 0.6 A reversed it is 43° the other way. Name two features of the data that support the claim that the current produces the magnetic field.
(1) The deflection is zero with no current and grows as the current grows (0°, 25°, 43°). (2) Reversing the current reverses the deflection with the same size (43° each way). A magnetized coil would deflect the needle even with no current and would not flip when the current reverses.
Question 17 of 20 · Short Answer
At a scrapyard, a crane's electromagnet lifts a car and drops it when the operator switches off the current. Explain this with the claim that a current produces a magnetic field, and describe a classroom test with a nail, a coil and paper clips that models it.
The current in the crane's coil produces a strong magnetic field that magnetizes and pulls the steel. With no current there is no field, so the car falls. Model: wind a coil on a nail, lift clips with the switch closed, then open the switch and watch the clips drop; repeat three times and include a trial with the switch open from the start (0 clips).
Question 18 of 20 · Short Answer
A coil connected to a meter gives a reading when a magnet is pushed into it. Describe a control trial that rules out the idea that moving the coil's wires or the meter causes the reading.
Move the coil and its wires the same way, at the same speed, with no magnet nearby, and repeat three times. If the meter reads zero, the wiring motion is not the cause, and the reading in the main trial comes from the changing magnetic field.
Question 19 of 20 · Short Answer
A magnet pushed into a coil gives +84, +90 and +87 µA. Pulled out, it gives -85, -88 and -83 µA. Find the two means and explain what the signs show.
Means: (84 + 90 + 87) ÷ 3 = +87 µA and (-85 - 88 - 83) ÷ 3 ≈ -85.3 µA. The opposite signs show that the current flows one way when the field inside the coil increases and the other way when it decreases: the direction depends on how the field changes.
Question 20 of 20 · Short Answer
In a simple microphone, a small coil attached to a thin membrane sits near a fixed magnet. Explain why a current flows in the coil only while there is sound, and predict what a louder sound (larger, faster membrane motion) does to the current.
Sound makes the membrane and coil move back and forth near the magnet, so the field through the coil keeps changing and an alternating current flows. With no sound the coil is still, the field does not change and there is no current. A louder sound moves the coil farther and faster, so the field changes faster and the current is larger.
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does HS-PS2-5 mean?
HS-PS2-5 asks students to plan and carry out investigations that show two things: an electric current produces a magnetic field, and a changing magnetic field produces an electric current. The focus is on the practice of investigating, so students design the tests and collect the evidence themselves. The code means High School, Physical Science, core idea 2 (Motion and Stability: Forces and Interactions), performance expectation 5.
Is HS-PS2-5 taught in physics or physical science?
It is usually taught in a high school Physics course, often in a unit on electricity and magnetism, and it also fits Physical Science or an integrated science course. Students need only basic circuits, magnets and means of repeated trials, so no algebra beyond averages is required.
What is the assessment boundary for HS-PS2-5?
Assessment is limited to designing and conducting investigations with provided materials and tools. Students plan with a given set of equipment rather than choosing anything they like, and they are not expected to calculate field strengths or induced voltages from formulas. HS-PS2-5 has no Clarification Statement.
What equipment do I need for HS-PS2-5 labs?
A low-voltage DC supply with a current limit (or cells with a switch and a power resistor), insulated copper wire, compasses, iron nails, steel paper clips, bar magnets and a sensitive meter. A center-zero galvanometer is ideal because it shows the direction of a small current. A voltage sensor on a data logger is useful for magnets dropped through a coil, but it is optional.
Is it safe to connect a wire to a battery for the compass experiment?
Only with something that limits the current. A bare wire across a battery is a short circuit: the current is large and the wire and battery can get hot enough to burn. Use a power supply with a current limit or a resistor in series, close the switch for a few seconds at a time, wear goggles and never use wall-outlet power.
Do students need Faraday's law or formulas for HS-PS2-5?
No. The formulas for the field of a wire and for induced voltage are beyond this standard. Students show the two relationships with evidence: what changes, what is measured and what the control trial shows. Teachers can still use the formulas privately to check that invented data sets are realistic.
What if my school does not have a galvanometer?
A digital multimeter on its most sensitive current or millivolt range works, although it may be too slow to catch a quick push. Use a coil with many turns (a few hundred) and a strong magnet, and push slowly enough for the display to update. For the first claim, a phone's magnetometer app can stand in for a compass.
How do you grade a student-designed investigation?
Use a short checklist: one independent variable; a measured dependent variable with units; at least two controlled variables; a control trial; repeated trials; a safety step; and a claim that cites the data. The homework rubric on this page gives two points for a complete plan and one point for a plan that misses the control or changes two things at once.
Why does Earth's magnetic field matter in these labs?
A compass always responds to Earth's field, so its reading with the switch open is the zero point for every trial. Keep steel objects and other magnets away from the compass during a trial.
What comes after HS-PS2-5?
HS-PS3-5 asks students to model two objects interacting through electric or magnetic fields, and HS-PS3-3 asks them to design a device that converts one form of energy into another, such as a small generator or motor. Both build on the evidence from HS-PS2-5 that currents and changing magnetic fields are linked.
07
Related Standards
6 standards
These standards connect to HS-PS2-5: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
MS-PS2-3Prerequisite
Ask questions about data on the factors that affect electric and magnetic forces
NGSS is a registered trademark of WestEd. Neither WestEd nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of this product, and do not endorse it.
