# Determine the resistance of Rl

## 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.

Ohms Law V=IR

## The Attempt at a Solution

becuase 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.

#### Attachments

• circuit.JPG
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rl.bhat
Homework Helper

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

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