How Things Work
How Do Smoke Detectors Work?
Smoke alarms detect airborne products of combustion rather than heat alone. Photoelectric alarms use a light source and sensor arranged so smoke particles scatter…
Oct 14, 2026 • 3 min readUNDERSTAND MORE
How Things Work
Explore the mechanisms behind familiar objects and complex systems, with explanations that connect individual parts to the whole.
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How Do Refrigerators Keep Food Cold?
A refrigerator does not manufacture cold. Its sealed vapour-compression system circulates a refrigerant through an evaporator, compressor, condenser and expansion device. The refrigerant absorbs heat as it evaporates at low pressure inside the cabinet,…
Oct 14, 2026 • 3 min readRead the discovery →LATEST
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New stories, explanations and research from How Things Work.
How Things Work
How Do Electric Kettles Know When to Turn Off?
Most basic electric kettles switch off when steam from boiling water travels through a channel to a thermostat near the base or handle. The…
Oct 14, 2026 • 3 min read
How Things Work
How Do Smoke Detectors Detect Fire?
Residential smoke alarms usually detect particles made by combustion rather than flames themselves. Photoelectric alarms shine light through a dark sensing chamber and trigger…
Oct 13, 2026 • 3 min read
How Things Work
How Do Automatic Doors Detect People?
Automatic doors commonly use microwave radar to detect motion approaching the entrance, active infrared sensors to measure reflections in a monitored zone, or both.…
Oct 13, 2026 • 3 min read
How Things Work
How Do Mechanical Pencils Work?
Most click mechanical pencils use a spring-loaded three-jaw clutch. Pressing the button pushes the clutch forward and opens its jaws, allowing the graphite core…
Oct 13, 2026 • 3 min read
How Things Work
How Do Induction Cooktops Work?
An induction cooktop sends alternating electric current through a coil beneath its glass surface. The coil creates a rapidly changing magnetic field, which induces…
Oct 11, 2026 • 3 min readWORTH KNOWING
Popular & evergreen
How Things Work
How Do Smoke Detectors Work?
Smoke alarms detect airborne products of combustion rather than heat alone. Photoelectric alarms use a light source and sensor arranged so smoke particles scatter…
Oct 14, 2026 • 3 min read
How Things Work
How Do Electric Kettles Know When to Turn Off?
Most basic electric kettles switch off when steam from boiling water travels through a channel to a thermostat near the base or handle. The…
Oct 14, 2026 • 3 min read
How Things Work
How Do Smoke Detectors Detect Fire?
Residential smoke alarms usually detect particles made by combustion rather than flames themselves. Photoelectric alarms shine light through a dark sensing chamber and trigger…
Oct 13, 2026 • 3 min read
How Things Work
How Do Automatic Doors Detect People?
Automatic doors commonly use microwave radar to detect motion approaching the entrance, active infrared sensors to measure reflections in a monitored zone, or both.…
Oct 13, 2026 • 3 min read