What's the resistance on the LED flashlight?
If 5 heads, the working current is 5*20mA=100mA=0.1A, the voltage at both ends of the resistor is 3-0.7=2.1V, so the resistance power is 2.1V*0.1A=0.21W., so the power of the resistor is 1/4W.From this, you can calculate the resistance power of 7 heads and 10 heads
If 3 heads (3 LEDs), the operating current is 3*20mA=60mA=0.06A, the voltage at both ends of the resistor is 3-0.7=2.1V, so the resistance power is 2.1V*0.06A=0.136W., so the power of the resistor is 1/4W.
LED is a light emitting diode, belonging to semiconductor lighting. A silicon PN section of the pressure drop is 0.7V, a light emitting diode operating current is 10--20mA, the battery general 2 section, voltage is 3V, light-emitting diode is commonly used in parallel
