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For example, if an electrical appliance is 380V to 220V, how is its current calculated? Is it 380V or 220V? If it is 220V to 12V?
Power is fixed, voltage decreases, current increases, voltage increases, current decreases, energy is constant
How many square copper wires are needed for 220 V transmission 1500 meters ballast 350 W
How many square copper wires does it need to transmit 1500m ballast at 220V to 350W?
Voltage drop less than 220 * 5% = 11V
S = 0.018 * 1500 * 300 / 11 * 220 = 3.9 square mm
According to the wire specification: 4mm2
Judgment: the current I in the conductor is directly proportional to the voltage u at both ends of the conductor and inversely proportional to the resistance R of the conductor
If it's right, isn't it against resistance and voltage and current?
Correct, current is related to voltage and resistance, but resistance has nothing to do with current and voltage, and resistance is related to material, cross-sectional area, length and temperature of conductor
As shown in the figure is the relationship between the current I and the voltage U of the two resistors A and B. connect them into the circuit in parallel
A. The current passing through a is greater than that passing through B. the current passing through a is less than that passing through B. the total resistance of a and B in parallel decreases with the increase of voltage at both ends. D. the total resistance of a and B in parallel increases with the increase of voltage at both ends
(1) It can be seen from the I-U image that when the voltages at both ends of resistance a and resistance B are equal and less than the voltage at the intersection, the current flowing through resistance a is greater than that passing through resistance B; when the voltage is greater than the voltage at the intersection, the current passing through resistance a is less than that passing through resistance B; therefore, when the two resistors are in parallel, the current passing through resistance a is greater than that passing through resistance B when the voltage is small, and the current passing through resistance a is greater when the voltage is large The current through a resistor is less than that through B resistor, so AB is wrong; (2) according to the image, the resistance value of B resistor R B does not change with the change of voltage, which is a fixed value; according to Ohm's law r = UI, with the increase of voltage, the current through a resistor increases more slowly, so the resistance value of a resistor R A increases with the increase of voltage, which is determined by the characteristics of parallel circuit It is known that if 1R union = 1R a + 1R B, then r union = r a r b r a + R B = R B 1 + r b r A. from R union = R B 1 + r b r a, it is known that with the increase of voltage u, R B remains unchanged, r a increases, then the parallel resistance R increases, so the total resistance of a and B increases with the increase of voltage at both ends, so C is wrong, D is correct; therefore, D is selected
RELATED INFORMATIONS
- 1. As shown in the figure is the relationship between the current I and the voltage U of the two resistors A and B. connect them into the circuit in parallel A. The current passing through a is greater than that passing through B. the current passing through a is less than that passing through B. the total resistance of a and B in parallel decreases with the increase of voltage at both ends. D. the total resistance of a and B in parallel increases with the increase of voltage at both ends
- 2. There is such a physics problem. When the voltage at both ends of a circuit is reduced to half of the original, and the resistance is increased to twice of the original, then the electricity passing through the circuit A the original quarter B the original half C the original double D cannot be determined
- 3. If a conductor is connected to a circuit and the voltage applied to both ends of the conductor is doubled, the resistance of the conductor and the current passing through it will be () A. The resistance and current remain unchanged. B. the resistance remains unchanged, and the current is twice the original. C. the resistance and current become twice the original. D. the resistance is reduced to half of the original, and the current is four times the original
- 4. When the voltage at both ends of the circuit remains unchanged, the resistance value increases by 2 Ω, and the current becomes 2 / 3 of the original value, what is the original resistance value
- 5. In a circuit with constant voltage, when the resistance is increased by 5 Ω, the current becomes four fifths of the original, then the original resistance is zero____ To change the current to the original value One third, another one should be connected in series______ The resistance of the sensor is high
- 6. The electricity meter of a classmate's home shows 052134 at the beginning of the month and 053032 at the end of the month, How many kilowatt hours of electricity does the student's family use in a month? How many joules is it equal to? If the price of electricity per kilowatt hour is 0.50 yuan, how much electricity will his family pay this month?
- 7. As the circuit shown in the figure, in the process of sliding plate P of sliding rheostat moving from end a to end B, the indication of ammeter () A. From big to small B. from small to big C. from big to small D. from small to big
- 8. How many watts and how many ohm resistance does it need to change 3.3 V DC power supply into 3.0 V DC power supply? The current is 1.4 to 1.5 a
- 9. With low-voltage DC power supply, the resistance of electrical appliances is constantly changing between 2000 ~ 6000 Ω. How to make a circuit with stable output current of 1mA? It is planned to use a single 9V or 12V battery as the power supply. The resistance value of the electric appliance changes greatly, so it is necessary to make 1mA current continuously pass through the electric appliance. It is better to add a regulating device so that the current can be adjusted between 1mA and 5mA, but when it is not adjusted, the current should be stable at a certain value, and the smaller the fluctuation is, the better. Under the premise of ensuring the current stability, the simpler the circuit is, the better Can lm334z with resistor and adjustable potentiometer achieve the goal? Why? Please explain the principle of constant current output of the circuit. If it is not convenient to explain, please give tips, such as telling me what concepts and principles I should understand to make this circuit
- 10. The open circuit voltage of a solar panel is 800 MV and the short circuit current is 40 ma If the battery board is connected with a resistor of 20 ohm to form a closed circuit, its terminal voltage is A.0.1V B.0.2V C.0.3V D.0.4V
- 11. How much current can a 4 square bv line withstand at 220 V voltage emergency How to calculate? There should be a formula
- 12. When an electric appliance is connected to a power supply after being connected in series with a 4 ohm resistance, the current of the circuit is 0.5A and the voltage at both ends of the electric appliance is 6V. The resistance of the electric appliance is Ohm and the voltage of the power supply is v
- 13. There are two resistors in parallel in the circuit, and the current flowing through the main circuit is 0.5A. If the resistance value of one resistor is increased by 10 ohm, If the resistance of the other resistor increases by 10 Ω, the current of the main circuit will decrease by 0.05A. Calculate the power supply voltage and the resistance of the two resistors!
- 14. A 4-ohm resistor is connected in series with a consumer on a 6V power supply. Now we only know that the actual power of the consumer is 2W, so the current passing through the consumer may be () A 2A B 1A C 0.5A D 0.25A how do I calculate B and C? Are they all right? Is this the question for senior high school entrance examination Big brother and big sister will come and help me. I'm in urgent need. Has anyone seen it? Tell me where it is in the middle school entrance examination
- 15. The resistance of an electrical appliance is 484 ohm, and the rated voltage is 220 v. how much work has been done by the current when the electrical appliance is connected to the circuit and works normally for 5 hours? How many kilowatt hours of electric energy is consumed?
- 16. A constant resistance is marked with 10 Ω 1 A. if it is connected to both ends of a 12 V circuit and works normally, how to connect a large resistance in the circuit? A constant resistance is marked with "10 Ω 1 a". If it is connected to both ends of a 12 V circuit and works normally, how to connect a large resistance in the circuit? If it is used in parallel with a resistor marked "20 Ω 1.5 a", what is the maximum voltage that can be applied to the circuit?
- 17. The working current of an electric appliance is 0.5 A, and it consumes 66000 J of electric energy in 10 min
- 18. The resistance of an electrical appliance is 120 ohm. How many ohm resistance should be connected in parallel with the electrical appliance to make 185 / 5 of the total current in the circuit pass through the electrical appliance? If the voltage at both ends of the electrical appliance is 185 / 5 of the total voltage, how many ohm resistance should be connected in series with the electrical appliance?
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- 20. In a series circuit, when there are multiple electrical appliances, how does the current change when one resistance is constant and one resistance is increased? Is the current of series circuit determined by the large resistance? Or is the resistance small?