Physics & engineering
Steady thermal conduction through a slab
Steady thermal conduction through a slab: Heat transfer rate = conductivity × area × temperature difference / thickness for one-dimensional steady conduction.
Physics & engineering — Page 2
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Physics & engineering
Carnot thermal efficiency limit
Carnot thermal efficiency limit: Maximum reversible heat-engine efficiency = (1−cold temperature/hot temperature) × 100, with absolute temperatures.
Physics & engineering
Wave propagation speed
Wave propagation speed: Wave speed = frequency × wavelength.
Physics & engineering
Thin lens image distance
Thin lens image distance: For the real-is-positive thin-lens convention, 1/f = 1/object distance + 1/image distance.
Physics & engineering
Snell’s law refraction angle
Snell’s law refraction angle: n₁sin θ₁ = n₂sin θ₂.
Physics & engineering
Sound intensity level
Sound intensity level: Sound intensity level = 10 log₁₀(intensity/reference intensity), in decibels.
Physics & engineering
Combine independent sound levels
Combine independent sound levels: For uncorrelated sources with the same reference, combined level = 10 log₁₀(10^(L₁/10)+10^(L₂/10)).
Physics & engineering
Coulomb electrostatic force
Coulomb electrostatic force: Signed interaction F = k q₁q₂/r² with k ≈ 8.9875517923×10⁹ N·m²/C².
Physics & engineering
Electric field from a point charge
Electric field from a point charge: Radial electric field = kq/r² with k ≈ 8.9875517923×10⁹ N·m²/C².
Physics & engineering
Uniform wire resistance
Uniform wire resistance: Resistance R = resistivity × length / cross-section area, converting mm² to m².
Physics & engineering
Energy stored in an inductor
Energy stored in an inductor: Stored magnetic energy = ½ × inductance × current² for a linear inductor.
Physics & engineering
Ideal transformer secondary voltage
Ideal transformer secondary voltage: Ideal secondary voltage = primary voltage × secondary turns / primary turns.
Physics & engineering
Pipe flow speed from diameter
Pipe flow speed from diameter: Velocity = flow in m³/s ÷ circular internal area.
Physics & engineering
Tank drain time from average flow
Tank drain time from average flow: Drain minutes = (volume − retained reserve) ÷ average flow.
Physics & engineering
Pump energy cost
Pump energy cost: Cost = input kW × hours/day × days × load factor × tariff.
Physics & engineering
Compressed air leak energy cost
Compressed air leak energy cost: Annual cost = leak flow × specific power × operating hours × leak factor × tariff.