An apparatus for applying an alternating electric field to a subject's body, the apparatus comprising: a plurality of capacitively-coupled sets of at least two electrode elements (52, 52'), each of the electrode elements (52, 52') having a dielectric layer; a support configured to hold the sets of electrode elements (52, 52') so that the dielectric layer of the electrode elements (52, 52') can be positioned in contact with the subject's body; and an electrical conductor; a plurality of temperature sensors, wherein each of the temperature sensors is positioned to sense a temperature at a respective one of the sets of electrode elements (52, 52') and generate a respective signal indicative of the sensed temperature; a plurality of electrically-controlled switches (56, 56'), wherein each of the switches (56, 56') is configured, depending on a state of a respective control input, either to allow current to flow between the electrical conductor and respective ones of the electrode elements (52, 52') or prevent current from flowing between the electrical conductor and the respective ones of the electrode elements (52, 52'); and a controller configured to control the state of the control input of each of the switches (56, 56'), wherein the controller is configured to accept, from each of the temperature sensors, the respective signal indicative of the sensed temperature the controller being configured to determine, based on the accepted signals, a speed at which the respective set of electrode elements (52, 52') heats up, the controller being configured to determine, based on the determined speed of heating up, a duty cycle at which the electrode elements (52, 52') of the respective set of electrode elements (52, 52') is to be driven, and periodically toggle the state of the control input of the switches (56, 56') that correspond to the electrode elements (52, 52') of the respective set of electrode elements (52, 52') at the determined duty cycle in order periodically to prevent current from flowing between the electrical conductor and the electrode elements (52, 52') of the respective set of electrode elements (52, 52'). a plurality of capacitively-coupled sets of at least two electrode elements (52, 52'), each of the electrode elements (52, 52') having a dielectric layer; a support configured to hold the sets of electrode elements (52, 52') so that the dielectric layer of the electrode elements (52, 52') can be positioned in contact with the subject's body; and an electrical conductor; a plurality of temperature sensors, wherein each of the temperature sensors is positioned to sense a temperature at a respective one of the sets of electrode elements (52, 52') and generate a respective signal indicative of the sensed temperature; a plurality of electrically-controlled switches (56, 56'), wherein each of the switches (56, 56') is configured, depending on a state of a respective control input, either to allow current to flow between the electrical conductor and respective ones of the electrode elements (52, 52') or prevent current from flowing between the electrical conductor and the respective ones of the electrode elements (52, 52'); and a controller configured to control the state of the control input of each of the switches (56, 56'), wherein the controller is configured to accept, from each of the temperature sensors, the respective signal indicative of the sensed temperature the controller being configured to determine, based on the accepted signals, a speed at which the respective set of electrode elements (52, 52') heats up, the controller being configured to determine, based on the determined speed of heating up, a duty cycle at which the electrode elements (52, 52') of the respective set of electrode elements (52, 52') is to be driven, and periodically toggle the state of the control input of the switches (56, 56') that correspond to the electrode elements (52, 52') of the respective set of electrode elements (52, 52') at the determined duty cycle in order periodically to prevent current from flowing between the electrical conductor and the electrode elements (52, 52') of the respective set of electrode elements (52, 52').