A computer serial port cable has a few requirements: the signal is 5 volts, and the total current flowing into the port can be up to 2 milliamps. If the current is too high, the circuit will be ruined. How much resistance must a serial cable have at 5 volts to keep the current below 2 milliamps?
If we have a circuit with a set resistance R, we want to change the voltage and measure the current. Which of the following shapes is our graph likely to have: