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  2. Wheel and axle - Wikipedia

    en.wikipedia.org/wiki/Wheel_and_axle

    The wheel and axle is a simple machine consisting of a wheel attached to the smaller axle so that these two parts rotate with each other in which a force is transferred from one to the other. The wheel and axle can be viewed as a version of the Lever , with a drive force applied tangentially to the perimeter of the wheel, and a load force ...

  3. Ohm's law - Wikipedia

    en.wikipedia.org/wiki/Ohm's_law

    Ohm's law states that the electric current through a conductor between two points is directly proportional to the voltage across the two points. Introducing the constant of proportionality, the resistance, [1] one arrives at the three mathematical equations used to describe this relationship: [2] where I is the current through the conductor, V ...

  4. Hydraulic analogy - Wikipedia

    en.wikipedia.org/wiki/Hydraulic_analogy

    Hydraulic analogy. Widely used analogy for explaining electrical circuits. Analogy between a hydraulic circuit (left) and an electronic circuit (right). Electronic-hydraulic analogies are the representation of electronic circuits by hydraulic circuits. Since electric current is invisible and the processes in play in electronics are often ...

  5. Electrical resistance and conductance - Wikipedia

    en.wikipedia.org/wiki/Electrical_resistance_and...

    The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is electrical conductance, measuring the ease with which an electric current passes. Electrical resistance shares some conceptual parallels with mechanical friction. The SI unit of electrical resistance is the ohm (Ω ...

  6. Electrical resistivity and conductivity - Wikipedia

    en.wikipedia.org/wiki/Electrical_resistivity_and...

    The SI unit of electrical resistivity is the ohm - metre (Ω⋅m). [1][2][3] For example, if a 1 m3 solid cube of material has sheet contacts on two opposite faces, and the resistance between these contacts is 1 Ω, then the resistivity of the material is 1 Ω⋅m. Electrical conductivity (or specific conductance) is the reciprocal of ...

  7. Rolling resistance - Wikipedia

    en.wikipedia.org/wiki/Rolling_resistance

    Wheel bearing rolling resistance is lowest with high axle loads and intermediate speeds of 60–80 km/h with a Crr of 0.00013 (axle load of 21 tonnes). For empty freight cars with axle loads of 5.5 tonnes, Crr goes up to 0.00020 at 60 km/h but at a low speed of 20 km/h it increases to 0.00024 and at a high speed (for freight trains) of 120 km/h ...

  8. Tractive effort - Wikipedia

    en.wikipedia.org/wiki/Tractive_effort

    The term tractive effort is often qualified as starting tractive effort, continuous tractive effort and maximum tractive effort.These terms apply to different operating conditions, but are related by common mechanical factors: input torque to the driving wheels, the wheel diameter, coefficient of friction (μ) between the driving wheels and supporting surface, and the weight applied to the ...

  9. Torsion spring - Wikipedia

    en.wikipedia.org/wiki/Torsion_spring

    A helical torsion spring, is a metal rod or wire in the shape of a helix (coil) that is subjected to twisting about the axis of the coil by sideways forces (bending moments) applied to its ends, twisting the coil tighter. Clocks use a spiral wound torsion spring (a form of helical torsion spring where the coils are around each other instead of ...