text: why do electronic instruments need to warm-up before use?   all the electronic equipments revolve around the electrons.. basically every gadget is made up of tiny transistors, fet etc.. each of these devices have their own cut-in voltage above which only they will be able to operate... this energy level is the energy at which electrons start to work, ofcourse this energy is released as heat...  the same example holds good for all exothermic chemical reactions as well