How can people take picture fpr black hole?

We actually cant, really. Black Holes are really very powerful and don't just happen in some random place in the cosmos. We have got shots of Black holes that you cannot even see, but all the other big black holes that look like something straight of a sci-fi movie that look real, are really just photo- shopped. good question. Hope This Helped.

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .