Here are (idealized!) current-voltage properties of a red LED and a green LED. 2

Question

Here are (idealized!) current-voltage properties of a red LED and a green LED. 20 E 15 0.5 Red LED voltage Vred/M Figure 1 Current-voltage of a hypothetical red LED. When the red LED is passing 20 milliamperes, the voltage across it is 1.8 volts 30 T 25 20 15 10 0.5 1.5 2.5 Green LED voltage vgreenMIVi Figure 2 Current-voltage characteristic of a hypothetical green LED. When the green LED is passing 20 milliamperes, the voltage across it is 2.2 volts. The forward voltage drop for the idealized red LED when it is conducting is 1.8 volts. The forward voltage drop for the idealized green LED when it is conducting is 2.2 volts.

Explanation / Answer

When 20mA passes through the red LED , it is switched on producing voltage of 1.8V across it. Which causes the green LED to be switched off.

When the green light is switched on at 20mA then the voltage across it is 2.2V but thus voltage causes red LED also to be switched on , so then the parallel combination takes 40mA current which is not possible according to KCL.

So only red LED will b ON nd Green LED will be switched off!!

Please post the next question separately.

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