I am struggling to understand why I can't get a full voltage range when I have the diode the correct way round. If you check this link:
If you look at the answer I have set my circuit up like circuit 2. I have a rheostat and have put the diode in parallel and I am using a 3V battery. When the diode is the wrong way round I get a range of 0-3V when I slide the rheostat. When it is the correct way round I only get 0-1V. When it is at 1V, the p.d. across the battery is still 3V. Where is this missing 2V? If I have connected the diode in parallel surely it must get the full voltage range (which it does in reverse bias but not forward)?