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As shown in the figure, line a is the U-I diagram line of a power supply, and line B is the U-I diagram line of resistance R. when the power supply and the resistance are used to form a closed circuit, the output power and internal resistance of the power supply are () A. 4W，1ΩB. 6W，1ΩC. 4W，0.5ΩD. 2W，0.5Ω
It can be seen from the figure that the electromotive force of the power supply e = 3V, short circuit current I = 6A; then the internal resistance R = EI = 36 Ω = 0.5A; when the resistance is connected with the power supply, the current in the circuit should be 2a, the terminal voltage is 2V, so the output power P = UI = 4W; so select C
The physical meaning of the intersection of power UI line and resistance UI line
It is the voltage and current value corresponding to the maximum power of electrical appliances in actual operation under such power supply
Ohm's law of closed circuit
High school physics elective 3-1 said: when the external circuit is disconnected, r = ∞, I = 0, IR = 0, u = E. but when I = 0, IR should also be = 0, that is, u = 0, so it is impossible to measure the electromotive force. What's the matter? Where R is the external resistance circuit, R is the internal resistance circuit, I is the current of the closed circuit, e is the electromotive force of the power supply_ ∩)o...
What I mean is: there is a formula e = IR + IR, if when I = 0, IR is equal to 0, uine = E. but what is deduced from the book is u = e, what's wrong with me?
Conceptual error
U refers to the external pressure, e is the electromotive force, if there is internal resistance, e = u + u when the circuit is closed
(U is internal resistance voltage)
So u = 0 doesn't mean e = 0
RELATED INFORMATIONS
- 1. Ohm's law in closed circuit U = E / R / R + I (to explain, u is the road voltage, e is the power electromotive force, e is the numerator, R / R + I is the denominator, R / R + I means the quotient of R divided by R plus I). How did this formula come out? Thank you!
- 2. Ohm's law of closed circuit Is the terminal voltage necessarily the power supply voltage? What are the internal resistance and external resistance? What are their differences and connections?
- 3. Calculation of maximum power of sliding rheostat by Ohm's law of closed loop If the sliding rheostat is connected in parallel with a resistor, how can the resistor be equivalent to the internal resistance
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- 10. In Cartesian coordinates, the distance OP from point P (- 2,3) to the origin=______ ．
- 11. The variation law of the terminal voltage U of a power supply with the resistance R of the external circuit is shown in figure (a), and the straight line of u = 12V in the figure is the asymptote of the line. Now, the power supply and a rheostat R0 are connected into the circuit as shown in Figure (b). It is known that the maximum allowable current of the power supply is 2a, and the maximum resistance of the rheostat R0 = 22 Ω (1) The results are as follows: (1) the electromotive force E and internal resistance R; (2) the output voltage range of a and B at no load; (3) the minimum resistance of a and B that can be connected to load
- 12. Ohm's law There are 6V 3W and 3V 1W bulbs, which are connected in series in a 9V circuit. In this paper, which bulb is connected with a resistor in parallel can make both lamps light normally. Why?
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- 15. Use resistance, sliding rheostat, power supply and ammeter to measure rated power of bulb The resistance is known
- 16. When using volt ampere method to measure resistance, it is found that the voltmeter and ammeter have small indication after closing the switch. What is the reason that the bulb is not on To see clearly, the ammeter and voltmeter have small indication and the bulb is not bright. The original title is written like this
- 17. I want to ask a question: if in the experiment, the corresponding current value and voltage value have been given, the resistance value can be obtained by Ohm's law If the results are very different each time, what may be the reason? For example, why are the results different when using a fixed circuit diagram to measure the resistance of the same small lamp? The reason why the resistance value changes is that it is always on for measurement. Does the resistance have a certain temperature? Thank you for your reply
- 18. When the resistance is constant, the greater the voltage, the greater the current (). When the voltage is constant, the smaller the resistance, the greater the current ()
- 19. It is proved by Ohm's law and the law of current and voltage in series circuit that R is always equal to R1 plus R2 Urgent need
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