Final answer:
The circuit for obtaining I-V characteristics of an LED should be set up by connecting a 100Ω resistor in series with the LED between the positive and negative terminals of a voltage source. An ammeter is placed in series with this circuit to measure current, and a voltmeter is connected in parallel with the LED to measure voltage.
Step-by-step explanation:
To complete the circuit setup for obtaining the I-V characteristics of an LED, you should connect the components between terminals X and Y as follows: First, connect the positive terminal (X) of the variable voltage source to one end of the 100Ω resistor. Next, connect the other end of the resistor to the anode of the LED. The cathode of the LED should then be connected back to the negative terminal (Y) of the voltage source, completing the circuit. To measure the current and voltage for the I-V characteristics, you will need to use an ammeter and a voltmeter.
For current measurement, place the ammeter in series with the circuit. This means it should be connected in the line between either the resistor and the LED or between the LED and the negative terminal of the power supply. For voltage measurement, connect the voltmeter parallel to the LED. Ensure that one probe is connected to the side of the LED that is connected to the resistor and the other probe to the side connected to the negative terminal of the power supply. This will allow you to measure the potential drop directly across the LED without the internal resistance of the voltage source affecting it, as terminal voltage is measured between these two points.