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Excuse me, I use 2 dry batteries 3V power supply. 12 2.4v-3v current 20mA led parallel. How many ohm resistance? Can let 12 led normal light!
Is the LED red or yellow? If not, 30 ohm resistor in series. If not, no resistor is required
I'd like to ask whether it's better to connect several 5 waste ordinary dry batteries in series or in parallel to power LED lamps?
If you can, I hope you can also tell me the power supply circuit,
Since it is a waste battery, its internal resistance must be very large, and the current it can provide is very small, so it can only be connected in series. Parallel connection will increase the current, but the old battery may not provide so much current. You can try, an LED is powered by two No. 5 batteries, and the current is about 10mA. You can calculate it according to this method
RELATED INFORMATIONS
- 1. The fact that one dry cell and two dry cells are used to supply power to a small light bulb, which one is brighter, shows that changing what can change the current in the circuit?
- 2. When the dry cell voltage is increased from 1.5V to 3V, how to increase the potential difference to increase the battery voltage? In other words, how to increase the potential difference is related to the electric field strength, and what determines the electric field?
- 3. Connect a dry battery, a small electric bead with a working voltage of 2.5V and a pencil lead with a length of 7cm to form a circuit as shown in the figure. Adjust the length of the pencil lead in the circuit just so that the small electric bead does not light up. Now you can strike a match and heat the pencil lead, and the small electric bead will light up later. Once the match goes out, the small electric bead will go out slowly. Here, the flame Like a switch, why can the flame play such a role?
- 4. Use a light bulb, a dry battery and a switch to make a self-made desk lamp. When the switch is off, the light bulb will be on. When the switch is closed, the light bulb will not be on. Draw the wrong circuit diagram Brother, help me. Please bring the picture Without a picture, please explain
- 5. The light bulb in the home circuit will be dimmed if it is used for a long time. The one that can make the light bulb brighter is a. replace it with a bigger light bulb. B. replace the dry battery of the flashlight C change to a new battery d change to a smaller bulb
- 6. The two dry batteries in the flashlight can only emit weak light after a long time. Take out the two dry batteries and measure them with a voltmeter. The voltage at both ends is close to 1.5V. Put them into the electronic clock and they can work normally. This phenomenon is explained by Ohm's law of closed circuit
- 7. What is the metal case of a flashlight equivalent to in a circuit?
- 8. How many Ω is the resistance of the filament when the flashlight bulb is emitting? How many Ω is the resistance of the copper wire used in the experiment, so it can be ignored
- 9. It is proved that the total resistance is equal to the sum of the resistances in series circuit
- 10. Is it correct that total voltage divided by total resistance equals total current in series circuit
- 11. Connect the same two dry batteries in series or in parallel, and then connect the same small bulb. Is the brightness of the small bulb the same?
- 12. The electromotive force and internal resistance of three dry cells in series (electromotive force of each cell is about 1.5V and internal resistance is about 0.3 Ohm) shall be measured with ammeter and voltmeter, A ammeter: range 0.6 a, internal resistance 1 ohm. B ammeter: range 3 A, internal resistance 0.2 ohm. C voltmeter: range 3 V, internal resistance 30 Ka ohm. D voltmeter: range 6 V, internal resistance 60 Ka ohm. E sliding rheostat 0 ~ 1000 ohm, rated current 0.1 A. f sliding rheostat 0 ~ 20 ohm, rated current 2 A. g wire key ······Why choose d instead of C voltmeter? Why should the ammeter in the experimental circuit be connected internally instead of externally? Should the ammeter be connected internally when measuring electromotive force?
- 13. When studying the relationship between current and resistance, the experiment is carried out with a fixed resistance of 5 Ω to make the indication of voltmeter 3 V, and then with a fixed resistance of 10 Ω A student didn't change the position of the slide vane of the sliding rheostat. After closing the switch, the voltmeter's indication will be () 3V (fill in "greater than", "less than" and "equal to"). Therefore, adjust the slide vane to () (fill in "left" or "right" note: reduce the resistance to the left and increase the resistance to the right), so that the voltmeter's indication will still be 3V (greater than) 3V; because the resistance and the sliding rheostat share voltage, the sliding rheostat resistance does not change, the resistance increases, the voltage will increase Adjust (to the right). Increase the resistance of the sliding rheostat, the voltage on the sliding rheostat will increase, and the voltage on the series resistance will decrease Why does the voltage of sliding rheostat increase when the resistance of sliding rheostat increases?
- 14. When the voltmeter measures the voltage, the voltage of the two dry batteries is exactly 3V, and the two ranges of the voltmeter are 0 ~ 3 and 0 ~ 15. Which range should be selected?
- 15. In the experiment of "measuring the rated power of small light bulb", it is known that the power supply voltage is 6V, the small light bulb is marked with "3.6V", and the filament resistance is about 12 Ω. The equipment used is as shown in the figure. The range of 0-15v of voltmeter is broken, the range of 0-3v is in good condition, and other equipment is in good condition. Xiaoming has connected some equipment. (1) from the figure, it can be seen that he reasonably selects the range of 0-0.6a of ammeter, and he The reason for choosing this range is ⊙___ (2) adjust the slide of the sliding rheostat. The reading of the voltmeter shows that the small bulb can light normally, but he doesn't know how to connect the voltmeter. Please connect the voltmeter to the circuit correctly with the stroke line representing the wire, and answer___ (3) move the slide to ⊙ before closing the switch___ End (fill in: "left" or "right"), the purpose of doing so is ⊙___ (4) after closing the switch, adjust the slide P. when the small bulb lights normally, the indication of the ammeter is 0.3A, then the rated power of the small bulb is ⊙___ W．
- 16. As shown in the figure, the specification of the small bulb is "6V & nbsp; 3.6W" (filament resistance does not change), close the switch, when the slide P of the sliding rheostat moves to the a end, the current indication is 0.6A; when the slide P moves to the B end, the voltage indication is 4V, then () A. The filament resistance of the small bulb is 6 Ω B. the power supply voltage is 10vc. The maximum resistance of the sliding rheostat is 10 Ω D. when the slide P is located at the B end, the power consumed by the sliding rheostat is 0.8W
- 17. A 10 ohm resistor, a 3V voltage source, a 3A current source. Series. Power A 10 ohm resistor, a 3V voltage source and a 3A current source. In series, what is the power of the current source? (the current direction of the current source is the negative pole of the voltage source)
- 18. The rated voltage of a bulb is 2.5V. Now, how to connect it to a 6V power supply Rated power is 5W) small light bulb can normally light up
- 19. If the filament of a light bulb has been used for a long time, will the resistance of the filament increase or decrease? Why?
- 20. There is a small light bulb. The resistance of the filament is 5 Ω when it lights normally, and the voltage required for normal operation is 2.5V. If we only have a 6V power supply, we need to make the small light bulb work normally______ The first resistance is______ The resistance in Ω