OpenStem

@openstem · Joined Jul 2026

7420 public items8 groups

Note~279 words · 1 min

Following a material through its whole life Every product is made from something that was mined, harvested or manufactured somewhere. Engineers think about the entire journey, not just the moment of manufacture. Designing so it CAN be recyc

Engineering

Engineering · L2 · Recycling & Material Life Cycles

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Note~198 words · 1 min

Engineering is a family, not a job Each branch focuses on a different kind of problem, and on a real project they work side by side. Rough test: if it pushes, spins or slides, it's mechanical. If it carries current, it's electrical. If a co

Engineering

Engineering · L2 · Which Engineer Builds What?

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Note~207 words · 1 min

Fixed pulley: direction only It's still worth having. Pulling DOWN using your body weight beats lifting UP with your arms. Movable pulley: force halved Block and tackle: stack the segments Reading MA off a diagram A crane operator at MA = 5

Engineering

Engineering · L2 · Pulleys & Mechanical Advantage

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Note~198 words · 1 min

Starting is harder than continuing Designing friction out The motivation is always the same: friction costs energy as heat and wears parts down. Designing friction in

Engineering

Engineering · L2 · Friction in Design

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Note~251 words · 1 min

A schematic is a connection map The symbols are international, so a schematic drawn anywhere can be built anywhere. The symbols to know Tracing a loop One path means the switch owns the whole circuit. Drawn open, the bulb cannot light howev

Engineering

Engineering · L2 · Reading Circuit Diagrams

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Note~274 words · 1 min

Making a magnet with electricity Any wire carrying current has a magnetic field around it, even a plain straight one. On its own that field is far too weak to be useful. The iron core Slide an iron bar inside the coil and the iron itself be

Engineering

Engineering · L2 · Electromagnets

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Note~367 words · 2 min

Three routes, and knowing which one is doing the work Wherever there's a temperature difference, heat moves from warm to cool. It just doesn't always take the same route, and spotting which one is active is the first step to speeding it up

Engineering

Engineering · L2 · How Heat Travels

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Note~245 words · 1 min

Pascal's principle Push on a sealed, trapped liquid and the pressure spreads equally to every surface it touches. Small piston in, big force out What you pay: distance Where it shows up Why liquid and not air

Engineering

Engineering · L2 · Hydraulics: Multiplying Force With Liquid

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Note~356 words · 2 min

A failure is information When something engineers built breaks, that's bad news and also the only way to learn certain things. So investigators dig in carefully rather than quietly rebuilding and moving on. The flaw that caused one failure

Engineering

Engineering · L2 · Learning From Failures

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Note~328 words · 2 min

The problem standards solve Imagine every factory chose its own bolt sizes. A bolt from one company would almost never fit a nut from another, every repair would need a custom part, and nothing could be swapped. A standard fixes that by get

Engineering

Engineering · L2 · Standards & Codes

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Note~360 words · 2 min

One end fixed, one end free A cantilever is supported at one end only and sticks out unsupported at the other. That single feature is the entire definition. What a load does to it Put weight on the free end and it bends down. Nothing undern

Engineering

Engineering · L2 · Cantilevers

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Note~272 words · 1 min

A different kind of storage A battery stores electrical energy. So does a capacitor, but it stores and releases it in a completely different way: instead of a slow trickle over hours, it can dump nearly everything it holds in an instant. Th

Engineering

Engineering · L2 · Capacitors: Quick Storage, Quick Release

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Note~323 words · 2 min

Evaporation takes heat with it Turning liquid into gas isn't free. Breaking the attractions holding liquid particles together takes energy, and that energy comes from whatever is nearby: the surface the liquid sits on, and the air around it

Engineering

Engineering · L2 · Evaporative Cooling

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Note~250 words · 1 min

Cleaning water, layer by layer Water from a river, lake or tap carries dirt, sand, leaves and dissolved compounds that taste or smell wrong. A filter forces it through layers of material, each catching something the others miss. Why one lay

Engineering

Engineering · L2 · How Water Filtration Works

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Note~353 words · 2 min

Write down what it must do, before you design it It's tempting to start sketching. But engineers gather requirements first: a written list of exactly what the finished design has to do. Without it a team can build the wrong thing for weeks,

Engineering

Engineering · L2 · Requirements Gathering

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Note~267 words · 1 min

Different prototypes answer different questions A prototype is a first try, but there's more than one way to build one. The right choice depends entirely on what you're trying to learn, and how much you're willing to spend to learn it. What

Engineering

Engineering · L2 · Comparing Prototyping Methods

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Note~119 words · 1 min

How a capacitor charges Connect an uncharged capacitor to a DC supply through a resistor and the voltage doesn't jump. It climbs, fast at first and then slower, never quite arriving. Drag τ. A small τ (low resistance or small capacitance) g

Engineering

Engineering · L3 · RC Charging in Action

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Note~265 words · 1 min

Bending moment A beam carries load across its length: a joist, a girder, a shelf. The internal turning effect trying to bend it is the bending moment. A diving board is a cantilever, so its maximum moment is at the fixed end. That's exactly

Engineering

Engineering · L3 · Beam Bending & Moment of Inertia

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Note~268 words · 1 min

Why a joint is solvable The sign convention Worked: a 3-member truss Each diagonal is a 3-4-5 slope, so sin = 0.6 and cos = 0.8. Check at joint C: each diagonal pushes up 0.6 × 500 = 300 N, and 300 + 300 balances the 600 N load exactly. Zer

Engineering

Engineering · L3 · Truss Analysis: Method of Joints

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Note~277 words · 1 min

Ohm's law Across most conductors, voltage and current are directly proportional. Resistance is the constant between them. Power, three ways Substitute Ohm's law into that and two more forms fall out: Why wires warm up Slide the current belo

Engineering

Engineering · L3 · Ohm's Law & Electrical Power

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Note~240 words · 1 min

Amplification: bigger, same shape What the chip does on its own That raw gain is unusable. Wire a feedback path from the output back to V− and it becomes precise. That's negative feedback. The two golden rules The non-inverting amplifier Th

Engineering

Engineering · L3 · Op-Amps & Basic Amplification

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Note~238 words · 1 min

Flow rate: how much, how fast The continuity equation For an incompressible fluid (water, oil, blood are all close enough), whatever goes in must come out. Nothing piles up or vanishes along the way. Sections 1 and 2 can be anywhere along t

Engineering

Engineering · L3 · Flow Rate & the Continuity Equation

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Note~365 words · 2 min

Why heat makes things bigger Atoms in a solid sit in a lattice, held by bonds that behave like tiny springs. Every atom is already vibrating. Add heat, they vibrate harder, and on average they sit slightly further apart. The whole object gr

Engineering

Engineering · L3 · Thermal Expansion & Material Behavior

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Note~323 words · 2 min

Nothing is best at everything Stronger usually means heavier. Cheaper usually means less durable. Faster usually means riskier. Engineering is deciding which of those matters most for THIS job, and accepting the bill for that choice. Constr

Engineering

Engineering · L3 · Design Trade-offs

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Note~352 words · 2 min

Why bother testing Every manufactured part has a spec: a target strength, size or behaviour. Quality control is the set of checks that confirms parts actually meet it before a customer sees them. Destructive versus non-destructive A tensile

Engineering

Engineering · L3 · Quality Control & Testing

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Note~318 words · 2 min

Torque is turning effect Whenever you turn a bolt, pedal a bike or push a door open, you're applying torque. It depends on two things together: how hard you push, and how far from the pivot you push. Why a longer handle helps τ = F × d mean

Engineering

Engineering · L3 · Torque & Wrenches

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Note~392 words · 2 min

One point that behaves like the whole object Every object has a centre of mass: the single point where you could treat all its mass as concentrated. Support it exactly there and it balances, whatever way up it is. The stability rule The bas

Engineering

Engineering · L3 · Center of Mass & Stability

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Note~397 words · 2 min

Charge stored: Q = CV Two conductive plates, an insulator between them. Apply V, collect Q. Drag the capacitance slider below. Charge climbs straight with voltage, and a bigger capacitor sits on a steeper line. Energy stored: E = ½CV² Charg

Engineering

Engineering · L3 · Capacitors & Energy Storage

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Note~195 words · 1 min

Digital means two states, nothing between A logic gate takes digital inputs and produces a digital output by a fixed rule. Three gates get you started. AND: everything must be true OR: one is enough NOT: flip it Wiring a real rule A door sh

Engineering

Engineering · L3 · Digital Logic Gates

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Note~337 words · 2 min

What c actually measures Specific heat capacity c is the energy needed to raise 1 kg of a material by 1 °C. Materials differ enormously: some heat up almost instantly, others soak up huge amounts of energy before their temperature moves. Kn

Engineering

Engineering · L3 · Specific Heat Capacity

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