The Oral Exam Experiment Worked

Last fall I posted that I was dropping homework from the grade book and adding an oral portion to every exam in the spring. Students were running Engineering homework problems through Gemini and handing in solutions they could not explain when I asked. I was grading a chatbot, so I stopped.

Spring semester is over. It worked. The oral portion runs about ten minutes per student. They pick one problem from their written work and walk me through it. Why mesh and not nodal. What the time constant tells you about the circuit. Where the negative sign came from. I learn more about what a student actually understands in that ten minutes than I used to learn from a semester of graded homework.

A new Lumina Foundation-Gallup study says 57% of US college students use AI in their coursework at least weekly, and one in five use it every day. At the same time, 53% say their school discourages or prohibits it. Daily use is highest among men and among business, tech, and engineering students. The students avoiding AI mostly cite ethical concerns and school policy, so the ones following the rules are falling behind on a tool they will use the rest of their careers.

My position on AI in education is simple. If we are preparing students for the jobs they are about to take, AI has to be in every class. Every engineering job they walk into will expect them to use these tools well. A program that prohibits AI is training students for a job market that no longer exists. The work is not to keep AI out of the classroom. The work is to teach students how to use it, where it fails, and when to check it against first principles.

That still leaves the assessment problem. If students use AI on everything, how do you know what they understand? You change how you measure them. Oral exams catch what written work cannot. In-class paper problems catch it. Hands-on labs, where a student wires a circuit on a breadboard, takes scope measurements, and explains what they are seeing, catch it cold. Take-home essays graded on polish do not catch anything anymore.

The AI can solve the circuit. It cannot explain why this student chose the loop they chose, and it cannot wire the breadboard when the lab is due at five. That is what we should be assessing, and that is the work employers are hiring for.

Car Buyer vs User

Image Google Gemini Generated

I stopped at a dealership recently to get some parts for my wife’s car and, as always, took a peek in the showroom. I ended up looking at stickers and counting the screens in a mid-range SUV. Four. One in the dash, one in the middle, one for the passenger, one in the back. A salesperson grabbed me and started walking me through them. I stopped paying attention about 30 seconds in. Paddle shifters, massage seats, gester controls, ten drive modes, ambient lighting, self parking, some kind of fragrance thing. I nodded. I would use none of it.

Apparently I am not alone. The JD Power 2024 Tech Experience Index rates the so-called advanced driver features near the bottom of what owners actually value. Gesture controls hit 43 problems per 100 vehicles, which is a polite way of saying they do not work. People pay for this stuff, give up on it, and then never bring it up again until they trade the car in.

I keep thinking about the iPhone in this context. Two billion of them have shipped. None came with a manual. Kids figure them out before they can read. Apple kept taking things away. The home button. The headphone jack. Each cut made the phone easier. Carmakers do the opposite. They keep piling features on and call it progress.

I drive a 2020 Tesla Model 3. The software is great. The maps work, the updates show up overnight, the menus make sense. The car also has a turn signal stalk, a gear stalk, and two scroll wheels on the wheel. Tesla removed all of those in the 2024 Highland refresh. You signal now by pressing a button on the spoke. You shift gears by swiping a slider on the screen. Owners are paying around $400 for aftermarket kits to put the stalks back in. Tesla rolled out a version in China with the stalk returned. The best software in the industry could not save the worst ergonomic decision in the industry.

A few years ago BMW went the other way and tried to charge for hardware. Eighteen dollars a month to turn on the heated seats already wired into the car. About 90 percent of BMWs leave the factory with the hardware in place. Customers were essentially being charged twice. BMW killed it in September 2023. New Jersey introduced a bill to make hardware paywalls illegal on cars, which tells you how badly that went over.

None of this is accidental. Cars get designed for the showroom because that is where the sale happens. Three knobs and two screens looks cheap next to haptic glass and 47 menu layers. Marketing wants the acronym count on the window sticker. So you walk in as a buyer, feel reassured by the complexity, sign, and drive home. About ten minutes later you become the user. The user wants the heat on without looking at a screen, the mirrors adjusted without a settings tree, and the left turn signaled with one finger (not that one! )

Things are starting to turn. Mazda kept the knobs and gets credit for it every time someone reviews the car. Volkswagen pulled the buttons, watched sales slip, and admitted in 2025 the buttons are coming back. Their design chief said the reversal is permanent. Euro NCAP is moving toward requiring physical controls on five core functions to keep a five-star rating, which means the regulators are about to do what the marketing departments would not.

The buyer is in the showroom for an afternoon. The best interface is one you do not have to think about, and you should not need a manual to signal a left turn.

DC, AC and GROUND Coupling Settings on the Oscilloscope

A student stopped me in lab last week. She was staring at a trace that kept drifting off screen. She had the coupling set to DC and a large offset was pushing her signal out of range. The question she asked was a good one: what is the difference between AC, DC, and ground coupling, and when do you use each?

The short answer is that coupling controls what the oscilloscope passes to its vertical amplifier before it draws anything on screen. With newer scopes from different manufacturers it is sometimes difficult to find where to set coupling so you can either hunt around (usually the way I do it!) or consult the user manuals.The choice changes what you see, and getting it wrong means you either miss something or start chasing a problem that is not there. Here's a pic with short definitions for each following.

DC Coupling

DC coupling passes everything through: the full signal including any DC offset. If you have a 10 mV sine wave sitting on top of a 12V supply, you see both. This is the correct default for most measurements. Power supply work, logic signals, anything where the offset carries information requires DC coupling. You want the complete picture. That student had the scope set to DC Coupling (often the default.)

AC Coupling

AC coupling inserts a series capacitor that blocks DC and attenuates frequencies below roughly 10 to 20 Hz, depending on the scope. That same sine wave now appears centered on zero, and you can use full vertical scale to examine it. This is useful for noise on a supply output, audio signals, or serial data eye diagrams where the DC level is irrelevant. The tradeoff is real: the capacitor charges and discharges, so the trace drifts for a few seconds after you switch modes. Square waves also suffer at low frequencies because the flat tops droop as the capacitor charges through the input impedance.

Ground Coupling

Ground coupling disconnects the input entirely and connects the vertical amplifier to ground. The signal disappears. You get a flat line at 0V. This is a calibration step, not a measurement mode. Use it to find your ground reference position before you connect a live signal, especially when you need to compare multiple channels on the same scale.

The student switched to AC coupling, centered the trace, and saw exactly what she wanted to see: about 80 mV of sine wave.

A Different Path to Quantum Computing Hits 99% Accuracy

Two research teams, one in Germany and one in Switzerland, published results in Nature on the same day showing quantum logic operations with better than 99% accuracy. The technique they used has been worked on for almost thirty years.

To get a quantum computer to do anything, you have to make individual atoms interact in a controlled way. Most neutral-atom companies do this by hitting atoms with lasers to push them into a high-energy state. The atoms interact, then the state decays quickly. The operation has to finish before the decay.

These two teams used a different method. They cooled lithium atoms to near absolute zero, trapped them in a grid made of laser light, and let neighboring atoms overlap slightly. No high-energy state needed. The atoms touch in a controlled, predictable way, and that touch becomes the logic operation. The ETH Zurich group and the Max Planck group used different control schemes and landed at similar fidelities.

The teams also reported Bell-state lifetimes over 10 seconds. A Bell state is a pair of qubits locked together so that measuring one determines the other, no matter how far apart they sit. The lifetime is how long that link survives before noise breaks it. Many quantum platforms measure this in microseconds or milliseconds. Ten seconds is a long window, and it matters because every gate operation has to finish before the link decays.

Lithium matters here for a specific reason. Its electrons follow a rule that no two of them can occupy the same state at the same time. That rule, built into the physics, prevents a whole category of errors automatically. The hardware handles some of the error checking that software would otherwise have to do.

The likely first use for machines like this is quantum chemistry. Simulating a drug molecule or a battery material means simulating how electrons behave. Lithium atoms in this setup follow the same rules as those electrons, so the hardware and the problem use the same physics. The phys.org writeup has details.