How does a heating pad work?

Heating pads contain heating elements that convert electricity to heat by passing current through a conductor (usually a wire). This process is variously referred to as resistive heating, ohmic heating, or Joule heating. The amount of heat generated is proportional to the square of the applied current multiplied by the resistance of the conductor. If SI units are employed (amperes for current and ohms for resistance) the unit of heat energyis called a joule.