What Is the Correct Resistance for Optimal LED Operation?

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SUMMARY

The optimal resistance for the LED circuit, where each LED has a switch-on voltage of 2V and operates at a current of 20mA, is determined by considering the total current drawn by the parallel configuration of three identical LEDs. The correct voltage across the resistor Rl is 9V (battery voltage) minus 2V (LED voltage), resulting in 7V. The total current for three LEDs is 60mA (20mA per LED multiplied by 3), leading to a required resistance of 116.67 ohms, calculated using Ohm's Law (V=IR).

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Homework Statement


All LEDs in the following circuit are identical. Each LED has a switch on voltage of 2V and draws a current of 20mA for optimal light production.

Determine the resistance of Rl that gives optimum operation for all LEDs.


Homework Equations


Ohms Law V=IR


The Attempt at a Solution


because the LEDs are connected in parallel I calculated the voltage for Rl to be 9-2 =7V then divided that by 20mA which gave me 350ohms, which is incorrect.
 

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Each LED draws 20 mA current. There are three LEDs. So the total current drawn from the battery is...?
 


OMG I am an idiot, I didn't read the question properly, I thought the 20mA was divided amongst the 3 LEDs. Haha, anyway Thankyou!
 

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