1. The problem statement, all variables and given/known data The circuit shown is used to produce a current-voltage graph for a 12V, 24W lamp: [Broken] http://img338.imageshack.us/img338/9139/circuitlu6.jpg [Broken] a) Calculate the resistance of the lamp in normal operation. b) Calculate the value for R which wold enable the voltage across the lamp to be varied between 0V and 12V. 2. Relevant equations P = IV V = IR 3. The attempt at a solution a) P=IV 24 = 12I I = 2A V = IR 12 = 2R R = 6 Ohms b) Absolutely no idea how to go about doing this... it seems that the voltage across the resistor R ought to be 8V, but I don't know, since we haven't been told what the component with the arrow pointing into the 24 ohm resistor is... Thanks for your help.