Let two similar rods of different metals ( say copper and iron ) are joined together and some current is let to flow . Is there a charge accumulation at the junction? 1. If so what is the cause of it and how do you distribute the charges ? 2. And also how did researchers (or scientists ) discover the accumulation of charges? 3. And also does it happen even if they are soldered (melted) at the junction? 4. One last one , does this case hold for same metals also?