MullOverThings

Useful tips for everyday

# Why do we put resistor after the LED?

## Why do we put resistor after the LED?

If the LED gets too much current flowing through it, it will burn out and die. So it always needs a resistor to protect it.

## Should resistor be before or after LED?

The resistor can be on either side of the LED, but it must be present. When two or more components are in series, the current will be the same through all of them, and so it doesn’t matter which order they are in.

## Where does the resistor go in an LED circuit?

Since this resistor is only being used to limit current through the circuit, it can actually be located on either side of the LED. Placing the resistor on the positive (anode) side of the resistor will have no differing effects from placing the resistor on the negative (cathode) side of the LED.

## What happens if you use an LED without a resistor?

When hooking up an LED, you are always supposed to use a current-limiting resistor to protect the LED from the full voltage. If you hook the LED up directly to the 5 volts without a resistor, the LED will be over-driven, it will be very bright for a while, and then it will burn out.

## When should you use a resistor?

The main function of resistors in a circuit is to control the flow of current to other components. Take an LED (light) for example. If too much current flows through an LED it is destroyed. So a resistor is used to limit the current.

## Which side of capacitor is positive?

To tell which side is which, look for a large stripe or a minus sign (or both) on one side of the capacitor. The lead closest to that stripe or minus sign is the negative lead, and the other lead (which is unlabeled) is the positive lead.

## Why is a resistor needed for LEDs?

A standard red LED usually has a voltage drop of around 1.7v, and so the value of the resistor can be chosen to pass 20mA at (voltage – 1.7). Assuming an input of 5v, this means a resistor that will pass 20mA at 3.3v, which (using Ohm’s Law) gives us an absolute minimum resistance of 165 ohms.

## What is the forward voltage of a resistor?

A typical forward voltage is 2V. In a circuit with a 9V battery, an LED, and a resistor, you will have 2V across your LED. The rest of the voltage – 7V – will be across the resistor. Ohm’s law tells you that current equals voltage divided by resistance. So if you have a 1000 Ohms resistor,…

## Can a resistor be used to control the current?

But you don’t have any way of controlling the current through the LEDs. It’s up to the internal resistance of the battery to decide the current. It could be high, it could be low. So it’s better to use a higher voltage and a resistor so that you take control of the current.

## How is current divided between a battery and a resistor?

In a circuit with a 9V battery, an LED, and a resistor, you will have 2V across your LED. The rest of the voltage – 7V – will be across the resistor. Ohm’s law tells you that current equals voltage divided by resistance. So if you have a 1000 Ohms resistor, you would get 7 divided by 1000 equals 0.007 – which is 7 mA.