i know that the p.d measured across XY is the p.d. across resistor B in this picture: http://img812.imageshack.us/img812/7665/68689848.png [Broken] But what if resistor B is removed like in this picture: http://img707.imageshack.us/img707/7798/41743055.png [Broken] What is the p.d across XY now? Is it 0? Anyone care to explain? Would greatly appreciate your help!