This paper introduces the 39th IPhO experiment test,which using the differential thermometer to measure the solidifying point of a crystalline solid substance and an efficiency of the solar cell.

• 第39届国际物理奥林匹克竞赛实验试题是:利用差示温度计法来测定固态晶体物质的凝固点和测定太阳能电池的效率。