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Does LED light switch when closed?
When the switch is “on” (closed), the current provided by the voltage source V1 flows to ground, so the LED does not turn on. Or you can think of it as the anode of the LED having 0V, like it’s cathode, therefore not turning on.
Is it a must to connect a resistor with an LED?
You have to connect a resistor in order to set the current that your LED is expecting. The resistor doesn’t need to be on the anode side, but it needs to be there (unless the voltage of the power supply is equal to or less than the voltage drop of the LED.)
Which switch must be closed to turn on the LED?
Switch S1 OR Switch S2 (or both of them) must be closed to light the lamp.
What happens to the led when the switch is off?
When the switch is “off” (open, like displayed in the schematic), the voltage source provides current to the led through the resistor, so it turns it on. Assuming the LED’s forward voltage is 2V, forward current is 20mA, the calculation for the resistor is as following:
How to turn off led when…?
When the switch is “off” (open, like displayed in the schematic), the voltage source provides current to the led through the resistor, so it turns it on. Assuming the LED’s forward voltage is 2V, forward current is 20mA, the calculation for the resistor is as following: V1 = I*R1 + Vf R1 = (V1 – Vf)/I = (12-2)/20m = 500Ohm
Why is limiting current into an led important?
Limiting current into an LED is very important. An LED behaves very differently to a resistor in circuit. Resistors behave linearly according to Ohm’s law: V = IR. For example, increase the voltage across a resistor, the current will increase proportionally, as long as the resistor’s value stays the same.
What should the current be for a led resistor?
Let’s say you are using the LED above with a supply voltage of 12V, an LED forward voltage of 3.9V, and a total forward current of 1400mA. What power rating should you choose for your resistor? The resistor has a voltage drop and so does the LED. So, according to Kirchoff’s Voltage Law: