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The voltage is 12 V and there is one 3mm diode. How much resistance do you need? How much resistance do you need for three diodes?
A diode needs 1K resistor in series
Three series resistors need about 500 ohm in series
Three in parallel, need series about 300 ohm resistance
What is the current of LED? How much resistance does it take to connect a three LED lamp with a voltage of 5 V
It's like asking how many watts are the bulbs? How much voltage do three bulbs need
Generally, the current required for 5mm diameter LED is between 10-20ma
The red voltage is 2.0V
The green voltage is 2.6V
The white voltage is 3.4V
If it's 5V, it's recommended that you connect each LED with a resistor separately. It's almost the same after 15mA according to the reference voltage
Other forms of LED, specific analysis
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- 1. When a bulb works normally, the voltage is 12 V and the resistance is 24 Ω. If the power supply voltage is 36 V, in order to make the bulb work normally, it is necessary to When a bulb works normally, the voltage is 12 V, and the resistance is 24 Ω. If the power supply voltage is 36 V, in order to make the bulb work normally, what is the resistance in series?
- 2. The bulb marked "6V & nbsp; 3W" is connected in series with an 18 ohm resistor and connected to a 9V power supply. What is the actual power of the bulb?
- 3. A 5V 2W bulb L is connected in series with a 10 ohm resistor R1, and then connected to a stable voltage power supply. The lamp l will light normally L and resistor R2 are connected in series and connected to the same power supply. The power of bulb L is 0.5W. Calculate the resistance of R2
- 4. The bulb marked 12v6w is connected in series with a 36 ohm resistor on a 12V power supply. What is the actual power of the bulb? What is the power consumed by the resistor at this time?
- 5. There is a small light bulb, when it is connected in series with a 40 ohm resistor and connected to a 6 V power supply, it can light normally. The small light bulb can light normally for 5 seconds, and the current works for 1 joule Calculate the rated voltage of the small bulb,
- 6. When a small bulb is electrified for 2 minutes, it consumes 240 J of electric energy. Please draw the circuit diagram to calculate the electric power of the lamp
- 7. 1. A lamp consumes 1kW of electricity in 25 hours. What is the power of this lamp? 2. How many hours can a 220V 50W bulb work with 1000W of electricity 1. A lamp consumes 1kW in 25 hours. What is the electric power of this lamp? 2. How many hours can a 220V 50W bulb work with 1000W electric energy? (detailed solution process and formula are required) 3. How much energy is consumed by a 110 V, 100 W electric appliance working for one hour? If the power ratio of a and B dual-purpose electrical appliances is 4:1 and the power on time ratio is 2:1, what is the power consumption ratio?
- 8. 220 V power supply is connected in series with a 25 W bulb and a 40 W bulb. The actual power of the last two lamps is calculated and the calculation formula is listed
- 9. There is an electric lamp, which consumes 100 watts when connected to the power supply. Connect it in series with another resistor and then connect it to the same power supply. The power consumed by the resistor is 9 watts. The strategy of bulb consumption at this time is proposed
- 10. The bulb L1 of "pz220-40" and the bulb L2 of "pz220-100" are connected in series in a 220 V circuit to calculate the actual power of the two lamps and compare which lamp is brighter? The bulb L1 of "pz220-40" and the bulb L2 of "pz220-100" are connected in series in a 220 V circuit to calculate the actual power of the two lamps and compare which lamp is brighter?
- 11. How big is the resistance of 5 white LEDs in parallel 12V battery? Repair a small lamp. The resistance is burned
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- 13. A physics problem: there are four resistances, R1 = 1, R2 = 2, R3 = 3, R4 = 4, e = 4V, r = 0.2, total current ——R1——R3—— | | | ——R2——R4—— | | ——||————— R1 and R3 are in one branch, R2 and R4 are in one branch, that is to say, they are connected in series and then in parallel, and there is another line between R1 and R3 and between R2 and R4 The general circuit diagram is like this. The lines in the diagram are all connected Is the middle line useless?
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- 17. Is electromotive force equal to supply voltage
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- 20. What is the difference between voltage source and current source? Voltage source and current source are the same power supply. I don't know the difference between them. Please answer in detail. Thank you!