#2RESISTORS in ELECTRONICS

To find the resistor value for a 5mm LED with a 12V DC supply, follow these steps:
Step 1: Determine the LED's Forward Voltage (Vf) and Current (If)
Typical values for a 5mm LED:
- Forward Voltage (Vf): 2-3V
- Forward Current (If): 20-50mA (usually 20mA for standard LEDs)
Step 2: Calculate the Resistor Value Using Ohm's Law
R = (Vsupply - Vf) / If
where:
- R = Resistor value (in ohms, Ω)
- Vsupply = DC supply voltage (12V in this case)
- Vf = LED forward voltage (assuming 2.5V for a typical 5mm LED)
- If = LED forward current (assuming 20mA = 0.02A)
Step 3: Perform the Calculation
R = (12V - 2.5V) / 0.02A
R = 9.5V / 0.02A
R = 475Ω
Step 4: Choose a Suitable Resistor Value
Since 475Ω is not a standard resistor value, choose the closest higher
value to ensure the LED doesn't receive too much current:
- 510Ω or 560Ω would be suitable choices
Step 5: Consider Power Rating and Tolerance
- Ensure the resistor's power rating can handle the dissipated power: P = (Vsupply - Vf) × If
- Consider using a resistor with a tolerance of ±5% or better to ensure accuracy

By following these steps, you'll find a suitable resistor value to safely
glow your 5mm LED with a 12V DC supply.

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