LED Electronics Basics

What is the consequence of connecting an LED in reverse orientation?

How is the appropriate resistor value calculated for a single LED when supplied voltage, forward voltage, and forward current are known?

According to Kirchhoff's Voltage Law for a series circuit, what does the total supply voltage equal?

What is the typical result of using a resistor value lower than what is calculated for the LED?

When connecting multiple LEDs in series, what step must be taken before calculating the required resistor?

What is the consequence of using a resistor that is too high in value when connecting an LED?

What does the term 'forward voltage' refer to in the context of LEDs?

When connecting multiple LEDs in series, which calculation is necessary before determining the required resistor?

Which of the following statements best describes Kirchhoff's Voltage Law in relation to LEDs?

What is a potential danger of connecting an LED in reverse orientation?

What happens if the calculated resistor value is applied in an LED circuit?

What is the typical value of a current limiting resistor needed when the supplied voltage is greater than the forward voltage of an LED?

LED Polarity and Position

LEDs have a positive anode (longer leg) and a negative cathode (shorter leg).
Incorrect polarity can damage the LED.

Current Limiting Resistors

Always use a current limiting resistor with LEDs to prevent excessive current and potential damage.
Higher current leads to brighter light, but excessive current will damage the LED.
Use a forward current rating suitable for continuous operation.

Calculating Resistor Value

Identify the supply voltage and the LED's forward voltage.
Add forward voltages for multiple LEDs in series.
Calculate the necessary resistor value using the formula: (Supply Voltage - Total Forward Voltage) / Desired Forward Current.
Round up to the nearest standard resistor value.

Example Resistor Calculation

Supply voltage: 9V
Forward voltage: 2V
Forward current: 20mA (0.02A)
Resistor Value: (9V - 2V) / 0.02A = 350Ω
Use a 360Ω standard resistor.

Typical Forward Voltage

Typical forward voltage is the voltage drop across the LED when operating.

Kirchhoff's Voltage Law

In a series circuit, the voltage drop across the resistor and LED equals the total supply voltage.

Switches

Switches do not have polarity.
Pressing the button closes the circuit, allowing current flow.
Releasing the button opens the circuit, stopping current flow.

Example Circuit Calculation

A yellow LED (2.1V) and an infrared LED (1.2V) in series:
Total forward voltage (Vf) = 2.1V +1.2V = 3.3V
Need to subtract that from the battery source
Divide by the continuous forward current to know the correct resistor.

This quiz covers the fundamental concepts of LED polarity, current limiting resistors, and how to calculate the appropriate resistor value for LED circuits. You'll learn about the importance of using the correct resistor to avoid damaging your LEDs and how to ensure they operate efficiently.