Abstract: Thermal characteristic of hot plate in alternating current ( AC) electric heater is studied, the heat transfer model is built and is solved by numerical method to find out the relationship between temperature and t ime.The results indicate:The periodicity of temperature completely matches with that of AC electric heating source, and its value just is half of the periodicity of AC electric voltage, that is τ_t =τ_q = 1/2τ_e .The effects of heat ing power ( q ) , periodicity of
heating source (τ_q ) , total heating capacity ( ρcV ) , heat exchange rate per 1 K ( aA ) on amplitude value are studied in detail.An amplitude number is defined, and a quantitat ive regression equation between amplitude and amplitude number is found.

Key words: alternating current, electric heater, heat transfer model, difference method, amplitude number