15 of 15 ideas
D.4 Induction: 15 ideas
Magnet drop speed and peak coil voltage
Research question. How does the release height of a magnet (0.05 to 0.50 m, 6 heights) affect the peak induced EMF in a 500-turn coil, and does the area under the EMF-time pulse stay constant?
- D.4 Induction
- HL topic
- Needs care
- Common: on 2 sites
My take. Very common (overdone), so it only works with the integration and speed check. The twist is measuring your own magnet's field to predict the area under the curve.
Method, physics and where marks are lost+
- Independent variable
- Release height above the coil, 0.05 to 0.50 m in 6 steps, each repeated 5 times. Speed at the coil is found from v = √(2gh) or from light gate timing.
- What you measure
- Peak EMF read from a voltage sensor and data logger (at least 1 kHz sampling). Area under each pulse is found by numerical integration to give the change in flux linkage.
- Controlled variables
- Same magnet and coil, so N and magnet strength are fixed. Same tube guiding the fall, so the path is centred. Same logger resistance and sampling rate. Magnet orientation kept the same every drop.
- Physics and graph
- Faraday's law, ε = −N dΦ/dt. Plot peak EMF against v (expect roughly linear) and integrated EMF against v (expect flat, equal to NΔΦ). The flat line is the real test of the law.
- SL and HL
- Induction is HL content, so this is an HL idea. Peak EMF against speed alone is a modest piece of work. Adding the integration, comparing it with a calculated NΔΦ from a measured magnet field, and explaining the asymmetric pulse (magnet accelerating) takes it to the top band.
- Where marks are lost
- Research design: assuming free fall speed when eddy current braking and tube friction exist. Data analysis: reading peak by eye from a low sampling rate and ignoring uncertainty in v. Evaluation: not addressing why the second pulse peak is larger than the first.
- Data
- Needs a coil, neodymium magnet and a fast data logger; the main uncertainty is the true speed at the coil and the sampling rate clipping peaks.
Coil diameter and acceleration of a coil in a magnet track
Research question. How does the diameter of a copper coil (10 to 25 mm, five sizes) of fixed turns affect its acceleration along a track of neodymium magnets on a battery-powered coil train?
- D.4 Induction
- HL topic
- Hard data
- Rarely listed
My take. Fun but messy. Only choose it if you measure current and resistance too, so that the explanation has real numbers.
Method, physics and where marks are lost+
- Independent variable
- Coil diameter, 10 to 25 mm in five or six steps, made by winding the same length of enamelled wire on different formers; 5 repeats each.
- What you measure
- Acceleration from video analysis in Tracker, using a metre rule in frame, in m/s²; resistance of each coil from a multimeter.
- Controlled variables
- Number of turns and wire gauge; battery type and charge state; magnet spacing on the track; mass of the train, adjusted with plasticine.
- Physics and graph
- Force on the current-carrying coil F = nBIL in the magnet field, with L the circumference. Larger diameter means more wire length in the field but higher resistance. Plot acceleration against coil circumference, with mass corrected.
- SL and HL
- Mostly HL, as induction and back emf are D.4. An SL student could treat it as force on a conductor (D.3) and stay at description. Top band models current with resistance and back emf.
- Where marks are lost
- Research design: mass and resistance change with diameter and are not controlled. Data analysis: acceleration from noisy position data. Evaluation: unreliable battery contacts.
- Data
- Needs Tracker, strong magnets and wire; the main uncertainty is friction and irregular coil contact with the magnets.
Coupled coils and how induced voltage falls with separation
Research question. How does the axial separation x (x = 2 to 20 cm in 2 cm steps) between two coaxial coils affect the peak voltage induced in a 200 turn pickup coil driven by a 1.0 kHz, 2.0 V signal?
- D.4 Induction
- HL topic
- Needs care
- Rarely listed
My take. A strong HL choice if you compare with the on axis formula rather than only fitting a power law. Measure the distance to the coil centres to avoid a hidden offset.
Method, physics and where marks are lost+
- Independent variable
- Separation x between the coil faces, 2, 4, 6, 8, 10, 12, 16, 20 cm, measured on a metre rule, three readings each.
- What you measure
- Peak to peak voltage in the pickup coil read from an oscilloscope, halved to give the amplitude.
- Controlled variables
- Driving frequency and amplitude: signal generator, checked on the scope. Coil alignment: coils on a rail or ruler so axes coincide. Coil size and turns: same pair throughout. Nearby metal: removed from the bench.
- Physics and graph
- Faraday's law: emf = −N dΦ/dt with emf = 2π f N B A. On the axis, a dipole model gives B ∝ 1/x³ for x much larger than the coil radius, so plot ln(V) against ln(x); the gradient should approach −3. For small x, use the full on axis loop formula.
- SL and HL
- Induction is HL only. At HL, top band work compares the data with the on axis loop formula B = μ0 I R² / 2(R² + x²)3/2 and shows where the far field power law starts to hold, and treats the effect of coil resonance.
- Where marks are lost
- Research design: no oscilloscope method described, so readings are vague. Data analysis: log graph gradient quoted without uncertainty and without saying over which range it was fitted. Evaluation: ignoring that x is measured from coil faces, not coil centres.
- Data
- Needs a signal generator, two coils and an oscilloscope; misalignment and measuring from the face rather than the centre are the main uncertainties.
Falloff of induced emf with coil separation
Research question. How does the peak induced emf in a secondary coil depend on its axial distance from a primary coil driven at 1.0 kHz, over separations of 1 cm to 12 cm?
- D.4 Induction
- HL topic
- Needs care
- Rarely listed
My take. A good HL choice with a rich log graph and a real model to test. Take it if your school has an oscilloscope, and make it yours by testing what the core material or coil orientation does.
Method, physics and where marks are lost+
- Independent variable
- Axial separation between coil centres, 8 to 10 values from 1 cm to 12 cm, measured with a ruler on a fixed track; 3 readings each.
- What you measure
- Peak to peak emf across the secondary coil measured on an oscilloscope. Optional calculation of the ratio to the primary voltage.
- Controlled variables
- Signal generator frequency and amplitude held constant and monitored on a second channel. Same coils, aligned on a common axis with a clamped track. No iron or metal nearby, and the secondary lead layout unchanged. Same oscilloscope range.
- Physics and graph
- Faraday's law: emf = -N dPhi/dt, with flux from the primary falling with distance, roughly like a dipole field, B proportional to 1/x3 for large separation. Plot ln(emf) against ln(x): the gradient gives the power law exponent.
- SL and HL
- Mostly HL because it relies on flux linkage and induction. A top answer compares the exponent to a model with two regimes (near field and far field) and explains why the exponent changes with x.
- Where marks are lost
- Research design: separations too coarse or coils not aligned. Data analysis: fitting one power law over a range where the behaviour changes. Evaluation: ignoring stray pickup and the coil's finite size when measuring x.
- Data
- Needs two coils, a signal generator and an oscilloscope; main uncertainty is defining coil separation and stray pickup at large distance.
Hand-cranked generator speed and peak voltage
Research question. How does the rotation frequency of a coil in a uniform magnetic field (1 to 8 Hz, 6 values) affect the peak e.m.f. of the generator?
- D.4 Induction
- HL topic
- Needs care
- Rarely listed
My take. Fine but a bit predictable. Make it personal by using a motor and a Hall probe to compare the B value you deduce with a direct measurement.
Method, physics and where marks are lost+
- Independent variable
- Rotation frequency of a coil, 1 to 8 Hz, controlled by a motor at set voltage or a hand crank with a marked rate. At least 6 frequencies, 3 readings each.
- What you measure
- Peak e.m.f. from an oscilloscope or datalogger, and frequency from the period of the trace, in Hz. Peak e.m.f. found from the trace amplitude.
- Controlled variables
- Coil area and number of turns. Magnetic field, by using the same magnets at the same spacing. Load resistance, using an open circuit or a fixed resistor. Brush contacts and their condition.
- Physics and graph
- e.m.f. = N B A ω sin(ω t), so peak e.m.f. = 2 pi N B A f. Plot peak e.m.f. against f; the gradient is 2 pi N B A, from which B can be extracted and compared with a Hall probe reading.
- SL and HL
- Induction is HL only. At HL, a straight line with a gradient that gives B. Top band: discuss the load effect on the terminal voltage, and the frequency read from the same trace so the data are self-consistent.
- Where marks are lost
- Research design: driving the coil by hand at an uneven rate. Data analysis: stating that the line proves proportionality without checking the intercept. Evaluation: ignoring slip ring noise and the change in loading at high speed.
- Data
- Needs a small generator kit, a motor and a scope or logger; the main uncertainty is the speed stability when turned by hand.
Induced emf from falling magnets of different strength
Research question. How does the peak emf induced in a 200 turn coil vary with the surface field strength of four to five magnets (about 20 mT to 400 mT), dropped from a fixed height of 0.20 m?
- D.4 Induction
- HL topic
- Needs care
- Rarely listed
My take. A good HL choice if you control size and mass carefully. The twist is to use the area under the trace, not just the peak, so that the physics goes beyond a simple comparison.
Method, physics and where marks are lost+
- Independent variable
- Magnet type, using ferrite, alnico and neodymium magnets of similar size, plus stacked neodymium discs (1 to 4) to give 5+ field values.
- What you measure
- Peak emf recorded with a data logger or oscilloscope, five drops per magnet. Field strength measured beforehand with a Hall probe at a fixed distance. Flux change estimated from the area under the emf against time trace.
- Controlled variables
- Drop height fixed with a clamped release tube. Same coil and same position in the tube. Magnet orientation with the same pole down. Magnets of similar mass, or mass recorded so speed differences can be corrected.
- Physics and graph
- Faraday's law, emf = -N dΦ/dt. Plot the area under the emf-time curve (which equals NΔΦ) against measured field strength; the gradient relates to the coil area and turns.
- SL and HL
- Faraday's law is HL, so this suits HL students. Top marks come from integrating the emf trace, checking that the area matches N times flux, and accounting for differences in magnet speed and mass.
- Where marks are lost
- Research design: changing several magnet properties at once, such as size and mass. Data analysis: reading only the peak and ignoring the area. Evaluation: not noting that speed changes with magnetic braking.
- Data
- Needs a logger or oscilloscope, a coil and a Hall probe; the main uncertainty is inconsistent drop and different magnet mass.
Induced pulse size for a falling magnet against coil turns
Research question. How does the peak EMF induced when a neodymium magnet falls from a height of 0.20 m through a coil vary with number of turns N from 100 to 1000 in 6 steps?
- D.4 Induction
- HL topic
- Needs care
- Rarely listed
My take. Worth doing at HL, but only with a logger. The pulse area test is the good bit.
Method, physics and where marks are lost+
- Independent variable
- Number of turns N: 100, 200, 400, 600, 800, 1000 (tap each tapping point on one long coil or use separate coils on the same tube), 5 drops each.
- What you measure
- Peak EMF from a datalogger or oscilloscope with a voltage sensor, sampling at 1 kHz or above. Also integrate the pulse area to find the total flux change.
- Controlled variables
- Drop height, fixed with a release stand and ruler. The same magnet throughout. Tube of same diameter and coil length, avoiding changes to the coil length as N changes by winding in layers. Coil resistance, checked by multimeter and noted.
- Physics and graph
- Faraday's law ε = −N dΦ/dt. Plot peak EMF against N: the gradient is the peak rate of flux change. The area under each pulse should be proportional to N with the same flux Φ.
- SL and HL
- Faraday's law is HL (D.4), so this is an HL idea. Top work uses the area under EMF against time to prove flux change is constant, and explains the asymmetric double pulse from the accelerating magnet.
- Where marks are lost
- Research design: using a multimeter for current, which cannot capture a millisecond pulse, so use a logger. Data analysis: reading peaks with too low a sample rate. Evaluation: not checking that layers of wire change the average area.
- Data
- Needs a logger with a voltage sensor and 1000 turns of wire; the main uncertainty is sample rate and magnet wobble in the tube.
Magnet fall height and peak e.m.f. in a coil
Research question. How does the release height of a neodymium magnet (5 to 50 cm, 6 heights) affect the peak e.m.f. induced in a 500 turn coil it falls through?
- D.4 Induction
- HL topic
- Needs care
- Rarely listed
My take. A good HL choice with clear physics. The twist is to check that the area under each pulse is constant, which gives an independent test of Faraday's law.
Method, physics and where marks are lost+
- Independent variable
- Release height above the coil, 5 to 50 cm, 6 or more values, using a guide tube and 5 drops each.
- What you measure
- Peak e.m.f. from a datalogger or oscilloscope connected to the coil, in mV. Speed at the coil from v = √(2 g h), checked by timing with a light gate.
- Controlled variables
- Magnet, the same one each time and dropped in the same orientation. Coil and number of turns. Circuit resistance and the input of the logger. Alignment through the centre of the coil, using a straight tube.
- Physics and graph
- Faraday's law: e.m.f. = N dPhi/dt, which depends on the speed of the magnet. Plot peak e.m.f. against v, or against √(h). The expectation is a straight line through the origin. Compare the area under the pulse with the total flux change, which should not depend on height.
- SL and HL
- Induction is HL only. At HL, plot peak e.m.f. against √(h) and integrate the pulse to check flux linkage. Top band: explain why the graph curves at high speed because of the finite length of the magnet and the coil's response.
- Where marks are lost
- Research design: dropping the magnet without a guide tube so it tumbles. Data analysis: reading a peak from a slow logger and missing it. Evaluation: not accounting for air drag or the magnetic braking from the coil itself.
- Data
- Needs a datalogger sampling at 1 kHz or more or a scope; the main uncertainty is the sampling rate and the tilt of the magnet.
Magnet falling through copper tubes of varying wall thickness
Research question. How does the wall thickness of a copper tube, from 0.5 mm to 3.0 mm, affect the time taken by a neodymium magnet to fall 30 cm through it, in seconds?
- D.4 Induction
- HL topic
- Needs care
- Rarely listed
My take. Visually striking and good physics, but sourcing suitable tubes is the catch. Personalise it by using a resistivity comparison with aluminium and brass tubes.
Method, physics and where marks are lost+
- Independent variable
- Wall thickness of copper tube, 5 or 6 values (for example stacked or nested tubes of the same inner diameter, or tubes of differing wall), each dropped 5 times. A plastic tube of the same size is the control.
- What you measure
- Fall time over a fixed 30 cm, measured with a phone slow-motion video at 240 fps or two light gates. Calculated: terminal speed = distance / time.
- Controlled variables
- Magnet: the same one each time, checked for mass. Tube length and inner diameter: measured with calipers. Tube orientation: vertical, checked with a plumb line. Temperature: tubes left to cool between drops.
- Physics and graph
- Faraday's and Lenz's laws: induced eddy currents oppose the motion, giving a drag that grows with wall thickness until saturating. At terminal speed mg = drag. Plot terminal speed against 1/thickness, or drag force mg against thickness, to test the trend.
- SL and HL
- Induction is HL content, so this is mainly an HL idea. Top band work explains the non-linear trend, since the field decays through the wall, and estimates drag from mg at terminal speed. Adding a second conductor such as aluminium widens the analysis.
- Where marks are lost
- Research design: getting varied wall thickness with tubes that also differ in inner diameter. Data analysis: timing errors from hand release and no video calibration. Conclusion: claiming a simple proportionality without testing it. Evaluation: not noting that the magnet may tilt or rub against the tube.
- Data
- Needs several copper tubes, a strong neodymium magnet and video timing; the main uncertainty is that tubes with different thickness are hard to source with the same bore.
Peak EMF against stacked magnets dropped through a coil
Research question. How does the peak EMF in a 500-turn coil vary with the number of identical disc magnets stacked together, from 1 to 6, when each stack is dropped from 0.15 m?
- D.4 Induction
- HL topic
- Needs care
- Rarely listed
My take. Fine at HL, but overlaps with turns idea. I would take this only if you also measure speed, which makes it your own.
Method, physics and where marks are lost+
- Independent variable
- Number of stacked neodymium disc magnets: 1, 2, 3, 4, 5, 6. Each stack dropped 5 times.
- What you measure
- Peak EMF recorded by a voltage sensor and datalogger. Also time between the two peaks to estimate the speed.
- Controlled variables
- Drop height and release method, using a stand. Coil turns and geometry, one coil throughout. Stack alignment and pole direction, all facing the same way. Tube friction, using the same smooth plastic tube.
- Physics and graph
- Peak EMF ∝ N dΦ/dt, with dΦ/dt rising with both field and speed. Plot peak EMF against number of magnets, and consider a speed correction since mass changes the fall through eddy currents.
- SL and HL
- Induction is HL, so this suits HL. Strong answers separate the effect of field from the change in speed by measuring the timing between peaks, and discuss why the relation is not exactly linear.
- Where marks are lost
- Research design: 'magnet strength' is not measured, so use the number of magnets and measure B with a probe if possible. Data analysis: ignoring speed change. Evaluation: magnets sticking or tilting in the tube.
- Data
- Needs a logger, a coil and neodymium discs; the main uncertainty is tilt and speed differences between stacks.
Peak EMF of a hand-spun coil against rotation frequency
Research question. How does the peak EMF induced in a 200-turn coil change as its rotation frequency is varied from 2 Hz to 10 Hz in steps of 2 Hz?
- D.4 Induction
- HL topic
- Needs care
- Rarely listed
My take. Worth choosing for HL if you can get a steady motor. A hand crank gives poor control, so the twist is to calibrate the motor first and extract B from the gradient.
Method, physics and where marks are lost+
- Independent variable
- Rotation frequency of the coil, 2, 4, 6, 8 and 10 Hz (5 values, 5 repeats each). Set by a motor driven at known voltages, with frequency measured by a phone slow-motion video or a light gate on the shaft.
- What you measure
- Peak EMF read from a data logger or oscilloscope connected across the coil via slip rings or brushes. Peak EMF is taken from each trace; the frequency is checked from the period of the trace.
- Controlled variables
- Number of turns and coil area: same coil throughout, measured with a ruler. Magnet strength and gap: same pair of magnets, fixed clamp position. Load resistance: use a high-resistance input on the logger so current is negligible. Orientation of coil axis: fixed in the frame.
- Physics and graph
- Faraday's law gives peak EMF = N B A ω, so EMF is proportional to frequency. Plot peak EMF (y) against frequency f (x); gradient = 2πNBA, so B can be extracted and compared with a Hall probe reading. Peak-to-peak EMF is not proportional to time-averaged values, so use the same measure throughout.
- SL and HL
- SL students can only do this as a descriptive test of proportionality with limited theory, since induction is HL. HL students derive the gradient, extract B, and compare it with an independent measurement. Top band work also checks the sinusoidal shape and discusses back-EMF and brush contact.
- Where marks are lost
- Research design: uncontrolled speed because the crank is turned by hand. Data analysis: measuring frequency poorly, no uncertainty on it. Evaluation: not explaining why the EMF trace is distorted or why the gradient differs from the predicted value.
- Data
- Needs a small motor or crank generator with a logger; the main uncertainty is the rotation frequency and brush noise.
Pipe resistivity and eddy current braking of a magnet
Research question. How does the resistivity of a vertical tube, using copper, aluminium, brass and other metals of the same dimensions, affect the fall time of a neodymium magnet dropped down it from a fixed height?
- D.4 Induction
- HL topic
- Needs care
- Rarely listed
My take. A classic that examiners know, but the resistivity angle with a real model is still good. Make it yours by varying the temperature of one tube to get a continuous IV.
Method, physics and where marks are lost+
- Independent variable
- Tube material (at least 5 tubes, e.g. copper, aluminium, brass, zinc-plated steel, plastic as control), converted to resistivity using tabulated values; 5 drops per tube. Better still, vary resistivity by measuring tubes at different temperatures with ice and warm water.
- What you measure
- Fall time over a fixed 40 cm section, measured with a slow-motion phone video at 240 fps or two light gates. Terminal speed v = distance/time and the estimated drag force are calculated.
- Controlled variables
- Same magnet and orientation, checked by a marker; tubes of matching length, inner diameter and wall thickness measured with vernier callipers; magnet released from the same height on the axis; tubes kept vertical with a plumb line.
- Physics and graph
- Induced emf ε = −dΦ/dt drives eddy currents I = ε/R, so drag force scales roughly as 1/ρ at terminal speed. Plot terminal speed v against ρ, or 1/v against 1/ρ; a straight line supports the model. Wall thickness also matters, so it must be matched.
- SL and HL
- An SL student can time falls and show that lower resistivity gives slower falls. Top band work builds a model for the terminal speed, tests the proportionality to ρ, and discusses why tubes of different wall thickness and magnetic permeability spoil the comparison.
- Where marks are lost
- Research design: tubes differ in wall thickness and diameter, so resistivity is not the only variable. Data analysis: only 3 materials used, so no meaningful graph. Evaluation: magnet tilting, sticking and ignoring the acceleration phase before terminal speed.
- Data
- Tubes of several metals are costly; buy offcuts or ask the school workshop, and use video analysis, which has an uncertainty of about one frame.
Step-down transformer: turns ratio versus efficiency
Research question. How does the secondary to primary turns ratio (0.25 to 2.0, six values) affect the output voltage and the efficiency of a demountable transformer supplied with 4.0 V AC at 50 Hz?
- D.4 Induction
- HL topic
- Easy data
- Rarely listed
My take. A safe, doable choice, but common in school labs, so the personal twist matters: for example, measure efficiency against load resistance too, or compare core materials. Take care to keep to low voltage.
Method, physics and where marks are lost+
- Independent variable
- Number of secondary turns Ns, with primary fixed at 200 turns: 50, 100, 150, 200, 300, 400 turns (ratio 0.25 to 2.0). Three repeats per setting.
- What you measure
- Secondary RMS voltage Vs and primary and secondary RMS currents, read with digital multimeters (AC). Efficiency = (Vs·Is)/(Vp·Ip) calculated for each ratio.
- Controlled variables
- Primary supply voltage (held at 4.0 V RMS, checked with a meter each time); load resistance (same resistor, e.g. 10 Ω, power rating checked); iron core and its clamping (same C-core and same tightness); supply frequency (fixed at 50 Hz from a low-voltage AC supply).
- Physics and graph
- Ideal transformer: Vs/Vp = Ns/Np, and power in equals power out. Plot Vs against Ns, expecting a straight line through the origin with gradient Vp/Np. Then plot efficiency against ratio to see where losses (copper, eddy currents, flux leakage) matter.
- SL and HL
- Induction is HL content, so an SL student could treat the ratio law as given but would struggle to justify it. HL depth comes from explaining the losses using Faraday's law and eddy currents, and from testing a laminated core against a solid one.
- Where marks are lost
- Research design: not stating the load and leaving primary voltage to drift. Data analysis: multimeter AC readings are unreliable with small currents, and uncertainty in efficiency is not propagated. Evaluation: blaming 'losses' without evidence for which loss dominates.
- Data
- Demountable transformer kit, low-voltage AC supply and two multimeters; the main uncertainty is meter accuracy on AC currents and coil resistance heating during a run.
Tube wall thickness or bore and magnet fall time in copper
Research question. How does the internal diameter of a copper tube (14 to 22 mm, 5 or more tubes) affect the time taken for a 12 mm neodymium magnet to fall 50 cm through it?
- D.4 Induction
- HL topic
- Needs care
- Rarely listed
My take. Popular and visual, but sources are hard to make consistent. Choose it only if you can find tubes with matching walls, and always include a plastic tube control.
Method, physics and where marks are lost+
- Independent variable
- Internal diameter of copper tubes of the same length and wall, 5 or 6 sizes from 14 to 22 mm, measured with a calliper. Five drops each.
- What you measure
- Fall time over the last 50 cm of tube from a video at 240 fps or light gates. Terminal speed = distance / time.
- Controlled variables
- Magnet, same one and orientation. Tube material and wall thickness, from the same supplier where possible. Tube temperature, since resistivity changes with it. Tube kept vertical using a plumb line.
- Physics and graph
- The falling magnet induces eddy currents that create a braking force, and at terminal speed the force equals its weight. A larger gap between the magnet and the tube wall weakens the coupling, so speed rises. Plot log v against log of gap, or v against the gap, and look at the trend; the exact law is not simple, so an empirical fit is needed.
- SL and HL
- Eddy currents and Lenz's law are in D.4, HL only. At HL, fit an empirical power law and discuss energy dissipated as heat. Top band: compare with a non-conducting tube control to show that the delay comes from induction alone.
- Where marks are lost
- Research design: only a few tube sizes with no control tube. Data analysis: fitting a straight line where the data are curved. Evaluation: tubes with different wall thickness and alloys changing conductivity as well.
- Data
- Needs copper tubes of several diameters, which can be costly; the main uncertainty is that tube wall thickness and purity vary between suppliers.
Winding temperature and transformer power efficiency
Research question. How does the winding temperature of a small step-down transformer, raised from 20 °C to 80 °C in steps of 10 °C, affect its efficiency, calculated as output power divided by input power?
- D.4 Induction
- HL topic
- Hard data
- Rarely listed
My take. Risky because the effect is small and easy to drown in noise. Worth it only if you can measure winding resistance directly with a four-wire method as a cross-check, and it needs low-voltage kit only.
Method, physics and where marks are lost+
- Independent variable
- Transformer temperature from 20 °C to 80 °C in 7 steps of 10 °C, each repeated 3 times. Heat in a water bath or with a hairdryer, or cool with ice, using a sealed or bagged transformer.
- What you measure
- Input and output r.m.s. voltage and current read with four multimeters (or two power meters), with efficiency calculated as Pout/Pin. Winding temperature taken with a thermocouple probe taped to the case.
- Controlled variables
- Load resistance fixed with one power resistor; input voltage held constant with a variable AC supply and monitored; frequency fixed at 50 Hz; measurement taken within seconds of switching on so self-heating does not drift the temperature.
- Physics and graph
- Winding resistance rises with temperature, R = R0(1 + αΔT), so copper loss I²R grows. Plot efficiency (or power loss) against temperature; the gradient links to α and the copper loss fraction. Requires transformer efficiency and induction ideas from D.4.
- SL and HL
- An SL student can plot efficiency against temperature and describe the trend. Top band work separates copper loss from core loss, extracts a temperature coefficient from the gradient and compares it with the accepted value for copper.
- Where marks are lost
- Research design: mains transformers are unsafe to heat and immerse, and self-heating during measurement is often ignored. Data analysis: efficiency changes are tiny, often smaller than meter uncertainty, and uncertainties are not propagated. Evaluation: the transformer core temperature is assumed equal to the case temperature.
- Data
- Needs a low-voltage bench transformer, four meters and a thermocouple; the efficiency change may be within meter resolution, so use the highest-resolution ranges.
Ideas were collected from public lists and published IA titles, merged when they are the same investigation, and rewritten from scratch. “On N sites” counts how many public lists carry the same investigation. How this list was made.
Frequently asked questions
What are good IB Physics IA ideas on electromagnetic induction?
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Good starting points with easy data that few sites list are step-down transformer: turns ratio versus efficiency. Each one gives a straight-line graph from school equipment, which is what the Data analysis and Conclusion criteria need.
Which electromagnetic induction IA ideas are overdone?
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None of the 15 ideas on this page appears on three or more public lists, so any of them is less likely to look like a copy.
Can I do a electromagnetic induction IA at SL?
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0 of the 15 ideas use SL physics. The others rely on HL-only content and are marked as HL topics.