Mechanical Equivalent of Heat Apparatus - TD-8551A



This Mechanical Equivalent of Heat Appara­tus provides an updated version of one of Joule's most important experiments, converting mechanical work to thermal energy.


  • Crank Counter -- Counts the number of turns on the handle.
  • Thermistor -- Embedded in the cylinder, it has lower thermal mass
  • Durable Construction -- Constructed primarily of steel and aluminum, there's virtually nothing to break. The thermistor is protected in the cylinder.


  • The base, cylinder, crank and counter with a built-in table clamp
  • 3.6 meters of flat nylon rope
  • A 1-gallon can that can be filled with a measured mass of sand or water (if 10 kg of laboratory masses are not available)
  • Laboratory manual including theory, step-by-step instructions and data tables
  • How It Works

    The apparatus is simple and accurate. Turn the crank to perform a measurable amount of work. The crank turns an aluminum cylinder. A flat nylon rope is wrapped several times around the cylinder. As the crank is turned, the friction between the rope and the cylinder is just enough to support a mass hanging from the other end of the rope. This ensures that the torque acting on the cylinder is constant and measurable. A counter keeps track of the number of turns of the crank.

    The work required to turn the cylinder is converted to thermal energy by the friction between the cylinder and the rope. The thermal energy is measured by monitoring the temperature of the cylinder using the embedded thermistor. The ratio between the work performed and the thermal energy produced and transmitted to the cylinder determines the mechanical equivalent of heat. With this apparatus, the equivalence of work and heat is easily established to within 5%.

    Buying Guide

    Basic Digital Multimeter
    Ohaus Triple-Beam Balance (with Tare)
    Basic Digital Multimeter   SE-9786A
    Ohaus Triple-Beam Balance (with Tare)   SE-8707
    Replacement Brush -- Mechanical Equivalent of Heat
    Replacement Cylinder -- Mechanical Equivalent of Heat
    Replacement Parts
    Replacement Brush -- Mechanical Equivalent of Heat   TD-8583
    Replacement Cylinder -- Mechanical Equivalent of Heat   TD-8582