Measure a suitable mass of liquid in say a Styrofoam cup (let's say 100 g). Place thermometer in cup along with heating coil. Be sure that resistance heater does not touch the sides of cup or the thermometer. Have ammeter in series with the resistance heater and voltmeter in parallel. Turn on heater and note the current, voltage and time to reach say 10 deg C above the starting temperature. Electrical energy in = heat energy gained by the system. Electrical energy = current x voltage x time (in seconds). Heat gained = specific heat of liquid x change in temperature x mass of liquid.
