LED Resistance: Learn Internal Resistance, Current Draw

In summary, the internal resistance of a LED is not fixed and depends on the voltage across it. Typically, a LED has a high resistance at low voltages, but as the voltage increases, the resistance decreases. The voltage at which the LED starts to draw current and glow is different for different types and colors of LEDs. To prevent the LED from drawing too much current, a series resistor is usually added. Without a resistor, a 5V voltage can cause the LED to draw a lot of current and potentially damage it. More information about LEDs can be found in the provided link.
  • #1
elecz
17
0
Can anyone tell me what is the internal resistance of LED? I mean is that very high or low? Usually how much current is drawn from it when it is given 5V?
 
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  • #2
LEDs and most other diodes are not really like resistors.

The current they draw depends on the voltage across them.

If you put a voltage on the anode that is positive relative to the voltage on the cathode, you can increase this voltage from zero and with a LED, a very small current will flow. (So, if you like, the device has a high resistance.)

As you increase this voltage, the LED current increases very slowly until a voltage is reached where the current starts to increase rapidly and the LED starts to glow.

This voltage is different for different types of LED and it is different for differnt colored LEDs. A red one may start to draw current and glow at about 1.3 volts while a white one may not draw much current until it gets about 3 volts across it.

Above this voltage, the LED starts to draw a lot of current and it is normal to put a resistor in series with it to limit the current it can draw.

If you did put 5 volts across a LED without a series resistor, it would draw a lot of current and probably melt the working part of the diode and it would not work after that.

You could say the apparent resistance of the LED would be very low with a large voltage across it.

You can read more about LEDs here:
http://en.wikipedia.org/wiki/LED
 

1. What is internal resistance?

Internal resistance refers to the resistance within a circuit component, such as an LED, that restricts the flow of current. It is caused by the resistance of the material used to make the component, as well as any other factors that may impede the flow of electricity.

2. How is internal resistance measured?

Internal resistance can be measured using a multimeter, which measures the voltage drop across a component when a known current is passed through it. The internal resistance can then be calculated using Ohm's Law (R = V/I).

3. Why is internal resistance important in LEDs?

Internal resistance is important in LEDs because it affects the efficiency and lifespan of the LED. A higher internal resistance can cause the LED to heat up and burn out more quickly, while a lower internal resistance allows for a more efficient flow of current and longer lifespan.

4. How does internal resistance affect current draw in LEDs?

The internal resistance of an LED affects the amount of current that can flow through it. A higher internal resistance means that the LED will draw less current, and a lower internal resistance will allow for a higher current draw. This can impact the brightness and overall performance of the LED.

5. How can internal resistance be reduced in LEDs?

One way to reduce internal resistance in LEDs is by using high-quality components and materials. Additionally, using proper circuit design and reducing the length of wiring can also help reduce internal resistance. It is also important to use the appropriate power source and avoid overloading the LED, which can increase internal resistance.

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