Hello, Madam. I have some doubts on your video ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-MvAAnNC2Lwk.html At time 6.17, you mentioned that the potential difference between the 2 voltage sources is 9V. However, there is no LOAD OR RESISTANCE between these 2 positive terminals of the two sources. So, why there is no short circuit in between these two terminals? If there is 9V difference, then there must exists some resistance? Similar issues at time 0.42. Please explain clearly. Thanks.