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When calculating the power of resistance and the current and resistance in closed circuit, why are the relevant formulas pure resistance If the non pure resistance does not conform to Ohm's law, please explain why
Joule's law calculates the thermal effect of electricity
If not pure resistance circuit
Then electric energy is converted into other forms of energy, such as electric energy is converted into mechanical energy by motor, and Joule's law is no longer applicable
The understanding of Ohm's law I = u / R can be considered from the definition of resistance. It is the obstruction of conductor to current. For the same resistance, the higher the voltage is, the greater the current can pass through. However, if it is not pure resistance, this part of electric energy will be converted into other forms of energy, that is, it is relatively difficult for current to pass through conductor, That is to say, the normal working resistance of the motor is equivalent to greater than its actual pure resistance, of course, Ohm's law is no longer applicable
How to calculate the resistance value when knowing the voltage, current and resistance power
Voltage 5V, current 3a to do a dummy load, resistance choose 0805, power 0.125, how to calculate the resistance? Ohm's law confused
To make a dummy load with 5V voltage and 3a current, the resistance value r = 5 / 3 = 1.67 Ω, but the power of the resistance needs 5 * 3 = 15W. Obviously, it is far from enough to select 0805 power and 0.125 power. If the resistance value is selected by 0.125w, the resistance value must be r = 25 / 0.125 = 200 Ω, while the current is only 5 / 200 = 0.025a, far less than
The voltage is 6.5V, how much resistance does it need to connect a green LED
150 ohm or 200 ohm resistance, 1 / 8 or 1 / 4 power, all OK
The voltage is 6.5V, how much resistance does it need to connect a white LED light
What are the current and voltage parameters of LED? LED is a current type device. The voltage of the same model is different, but the current is the same. You can get the parameters at the place where you buy it. Calculate the resistance and power according to the series circuit, and make sure that the current does not exceed the given parameters. Otherwise, the LED will light up in advance
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- 2. Using 5.5V voltage with 3V 20mA LED bulb resistance value Should I use a resistor with U / I = R (5.5 / 0.02 = 275), or a resistor with (input voltage output voltage) / current = (5.5-3) / 0.020 = 125 ohm, or some other resistor? Give me a value and the solution to this problem in the future,
- 3. How much resistance does it take to connect 1 LED (light emitting diode) in series with 24 V voltage
- 4. The voltage at both ends of the small bulb is 3.8V, and the current passing through is 0.3A. Within 10min, the current does work on -- J and consumes -- J's electric energy To get the formula, the process
- 5. If the light bulb is short circuited, does the voltmeter and ammeter show the number?
- 6. What is open circuit, short circuit, open circuit? How to know whether the bulb is short circuit or open circuit? What about the series connection of voltmeter? What about the parallel connection of ammeter? It's junior high school science knowledge
- 7. In the series circuit, a bulb short circuit or open circuit, how does the voltmeter and ammeter change, and in the parallel circuit, how does the ammeter and the voltmeter change
- 8. The ammeter is out of order. There is a voltmeter. How to measure the rated power of the bulb
- 9. When measuring the electric power of small bulb, considering that the ammeter and voltmeter have certain resistance, should the measured value of electric power of small bulb be larger than the real value
- 10. Xiaohong and Xiaowei have done the experiment of "measuring the electric power of small light bulb". There are two kinds of power supply (voltage is 6V), voltmeter, ammeter and sliding rheostat (a is marked with "50 Ω & nbsp; & nbsp; 2A", B is marked with "20 Ω & nbsp; & nbsp; It is known that the rated voltage of the two small lamps are 2.5 V and 3.5 V respectively, and the rated current is the same. They choose the equipment to carry out the experiment. Xiaohong connects the circuit correctly, connects a small lamp into the circuit, closes the key, moves the slide of the rheostat, and observes that the small lamp lights normally when the slide is near the midpoint. The ammeter shows the following As shown in the figure. ① during the experiment, the rheostat selected by Xiao Hong is______ (choose "a" or "B"), the rated voltage of the lamp she measured is______ V, rated current of______ Please calculate the rated power of Xiaohong and Xiaowei according to the relevant information______ (write the calculation process)
- 11. When a resistor is connected to a circuit, the consumed power is 110W. When 3C charge is passed, 330j of electric energy is converted into internal energy, then () A. The voltage applied to the resistor is 330vb. The current through the resistor is 1Ac. The power on time of the resistor is 3SD. The resistance value of the resistor is 110 Ω
- 12. Why is the total electric power divided by the supply voltage not equal to the circuit current in a series circuit? Why is the power divided by the voltage not equal to the circuit current?
- 13. How to calculate the total power when the current and voltage of three-phase electricity are known/
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- 15. When two resistors are connected in parallel, please tell us the distribution law of their current and electric power
- 16. In the home circuit, what is the device that shows how much electricity is used?
- 17. Problems in the chapter of home circuit in Physics There is a voltage of 220 V between the live line and the zero line, not between the zero line and the ground, and not between the ground and the ground. Why? It is said in the book that the zero line is connected to the ground, and then the ground is grounded. I don't quite understand. Who can explain this voltage. But isn't the home circuit AC? Can't the current pass through the zero line? At this time, it has no voltage? And, Is it OK to touch the zero line when you get an electric shock? Does the zero line also have current? It's better to have a circuit diagram to explain If the zero line forms a loop with the live line, why does it have no voltage and current
- 18. When the switch is closed, the light doesn't work, but the fuse is blown immediately. The reason for this phenomenon may be () A. There is an open circuit somewhere in the circuit B. connect one end of the switch to the neutral line and one end to the live line C. connect the switch to the neutral line D. the voltage in the circuit is too low
- 19. Exercises of physical circuit diagram in grade three of junior high school
- 20. If the filament of the bulb in the home circuit is broken, and the insulation of the wire is damaged, you should choose the method of maintaining the circuit A. Replace the bulb B. replace the fuse C. replace the wire and connect it D. replace the switch