# Which side of the LED is positive?

Diode and LED Polarity. Diodes only allow current to flow in one direction, and they're always polarized. A diode has two terminals. The positive side is called the anode, and the negative one is called the cathode.
A.

### What resistor do I need with an LED?

Choosing a resistor to work with an LED is fairly simple, but does require some knowledge of the LED and a small amount of maths. Some LEDs such as colour changing LEDs, flashing LEDs and 5V LEDs are designed to run off a 5V supply and therefore don't need a resistor.
• #### What is the forward current of a LED?

The forward current of an LED, IF, is the current which flows across the LED's leads, from anode to cathode, in order for the LED to receive sufficient current to power on. As you can see above, positive voltage must be applied across the LED from its anode to its cathode.
• #### How do you read the value of a resistor?

Steps
1. Position the resistor with the gold or silver color band to the right..
2. Read the color sequence that must be decoded to determine resistance.
3. Determine the coded number for the resistive value.
4. Determine the tolerance of the resistor.
5. Determine the decoded number for the resistive value.
• #### Are diodes and resistors the same?

A diode allows current to only flow in one direction. A resistor is essentially a load where higher resistance reduces current flowing in a circuit based on ohms law which says Voltage = Current x Resistance. So if Voltage remains constant and resistance increases, Current decreases.
B.

### What voltage to use for LED?

Many circuits operate LEDs at less than the recommended maximum current, to save power, to permit the use of a standard resistor value, or to reduce brightness. Typically, the forward voltage of an LED is between 1.8 and 3.3 volts. It varies by the color of the LED.
• #### What is a driver for LED?

An LED driver is an electrical device which regulates the power to an LED or a string (or strings) of LEDs. An LED driver responds to the changing needs of the LED, or LED circuit, by providing a constant quantity of power to the LED as its electrical properties change with temperature.
• #### What is the forward current of a LED?

The forward current of an LED, IF, is the current which flows across the LED's leads, from anode to cathode, in order for the LED to receive sufficient current to power on. As you can see above, positive voltage must be applied across the LED from its anode to its cathode.
• #### What is the use of LED?

Early LEDs were often used as indicator lamps for electronic devices, replacing small incandescent bulbs. They were soon packaged into numeric readouts in the form of seven-segment displays and were commonly seen in digital clocks.
C.

### Why is it necessary to use a resistor in series with an LED?

The ballast resistor is used to limit the current through the LED and to prevent that it burns. If the voltage source is equal to the voltage drop of the LED, no resistor is required. The resistance of the ballast resistor is easy to calculate with Ohm's law and Kirchhoff's circuit laws.
• #### What is the wattage of a resistor?

The wattage is the amount of energy the resistor can dissipate without failing. This depends on your application, but use Joule's Law of P = I * I * R. If your circuit operates at 50mA and the resistance is 330 Ohms, the power dissipated by the resistor is 0.825 Watts.
• #### How do you read the value of a resistor?

Steps
1. Position the resistor with the gold or silver color band to the right..
2. Read the color sequence that must be decoded to determine resistance.
3. Determine the coded number for the resistive value.
4. Determine the tolerance of the resistor.
5. Determine the decoded number for the resistive value.
• #### Do diodes have a resistance?

The ideal diode has zero resistance for the forward bias polarity, and infinite resistance (conducts zero current) for the reverse voltage polarity; if connected in an alternating current circuit, the semiconductor diode acts as an electrical rectifier. The semiconductor diode is not ideal.

Updated: 3rd October 2019