I have read about thermoelectric effects such as the Seebeck effect, the Peltier effect, and the Thomson effects. I understand that if there is a temperature difference between two ends of a metal, then in the hot junction end electrons will move more vigorously than in the cold end junction and then electrons will move from hot to cold junction and eventually there become a difference in potential between the hot and the cold junction and if I connect it with a wire a current will flow.
But Seebeck says that when two dissimilar metals are being coupled and put one end in hot and another in cold junction then only an EMF will be produced.
But I don't understand previously when I used only one type of metal then also an EMF was generated, then why do I need to couple two dissimilar metals? What is the importance to couple two dissimilar metal to have an EMF in circuit?