![](data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 72 71" width="72"></svg>)
It is difficult to connect the 220V 100W and 220V 40W A and B in series to the 440V power supply a. They all glow normally b. The nail may burn out c. It may be burnt out d. The current works as much on the light
B may be burnt out,
Because the rated current of B is 0.1818 and that of a is 0.4545
When a and B are connected in series to the 440V power supply, the actual current is 0.2597, which is far more than the rated current of B. therefore, if C is selected, B may burn out
Given that ABCD is four different rational numbers, and (a + C) (a + D) = 1, (B + C) (b = D) = 1, find the value of (a + b) (b = C)
Analysis: (a + C) (a + D) = 1, (B + C) (B + D) = 1
Construction equation (x + C) (x + D) = 1
The equation is expanded and sorted out: X & sup2; + (c + D) x + CD-1 = 0
According to Weida's theorem, a + B = - (c + D) is a + D = - (B + C)
∴(a+c)(b+c)=-(a+c)(a+d)=-1
1. The electromotive force E of a DC power supply is 10V. The internal resistance R0 is 1 ohm. When the external resistance forms a closed circuit, what is the maximum power consumed by the external resistance?
The derivation is as follows: P = [E / (R0 + R)] ^ 2R, the numerator and denominator divide by R at the same time, the numerator becomes e ^ 2, the denominator becomes R0 + R + R0 ^ 2 / R, according to the basic inequality, R + R0 ^ 2 / R ≥ 2r0, if and only if R0 = R, the external power is the largest. Therefore, the maximum power of external resistance is 25W
Finding the differential dy of the function y = TaNx + X & # 178
dy=y'dx
=(1+tan^2x+2x)dx
Air switch single phase meter wiring diagram
How to connect a single meter from the small air switch? 1. It's the live wire incoming line, 2. It's the live wire outgoing line. The incoming line comes down from the air switch. Where should the live wire from the meter go?
The electric energy meter needs to be connected with voltage and current. The hot wire coming in and out is to connect the current. The hot wire coming out is connected with the load (electrical equipment). In addition, it needs to be connected with the zero wire to make the meter collect the voltage between the hot wire and the zero wire
Find the value of the algebraic formula X & # 178; (x-1) - x (X & # 178; + x-1), where x = - 1 / 2 (negative half). Thank you for your prompt answer
x²﹙x-1﹚-x﹙x²+x-1﹚
=x³-x²-x³-x²+x
=-2x²+x
When x = - 1 / 2
simple form
=-1/2-1/2
=-1
Under the standard condition, 500 volumes of HCl are dissolved in 1 volume of water to reach saturation, and the density of the solution is pg / ml, then the mass concentration of the solution is (mol / L)
n(HCl)=500/22.4
V=(1000 + 36.5*500/22.4)/p mL
c=n/V(L)
This is the answer on the Internet. Where did 1000 come from?
You can assume that 500 l of HCl gas is dissolved in 1 l of water
Then the amount of solute = 500L / 22.4l/mol
Mass of solution = mass of solvent + mass of solute
=1000g + 500L/22.4L/mol*36.5g/mol
Volume of solution = mass / density of solution = (1000 + 500 / 22.4 * 36.5) / P (ML)
Finally, the volume of the solution is converted into liters, and the concentration of the substance can be obtained
Let "△" be a new operation rule, 2 △ 3 = 2 + 3 + 4 = 9, 5 △ 4 = 5 + 6 + 7 + 8 = 26 According to this rule: 7 △ 5=______ ．
According to the meaning of the question: 7 △ 5, = 7 + 8 + 9 + 10 + 11, = 45
As shown in the figure, there is a small bulb with a rated voltage of 2.4V. The resistance of the small bulb is 8 Ω when it works normally. If we only have a 3V power supply, how large a resistance needs to be connected in series to make the small bulb work normally?
The current in the circuit I = ulrl = 2.4v8 Ω = 0.3A, the voltage at both ends of the resistor ur = u-ul = 3v-2.4v = 0.6V, so the resistance value of the series resistor R = URI = 0.6v0.3a = 2 Ω. A: a 2 Ω resistor needs to be connected in series
4 - (- 2) ^ 3-3 ^ 2 ÷ (- 1) ^ 2N-1 + 0 * (- 2) ^ 3 Calculation
4-(-2)^3-3^2÷（-1）^2n-1+0*（-2）^3
=4+8-9÷（-1）＋0
=12+9
=21
RELATED INFORMATIONS
- 1. As shown in figure a is the circuit diagram of "measuring the rated power of small bulb", the power supply is two dry batteries; the small bulb is marked with the word "2.5V", the resistance is about 10 ohm, and it is slippery
- 2. Does dry battery convert electric energy into chemical energy or chemical energy into electric energy? The answer is that chemical energy is converted into electrical energy. Why? I can't figure it out! I always think that electrical energy is converted into chemical energy
- 3. A resistance R to be measured and current a are connected in series in the circuit shown in the figure. At this time, the indication of the ammeter is I1. If a constant resistance R0 with known resistance value is connected in series in this circuit, the indication of the ammeter becomes I2. According to the above data, the resistance value of the resistance Rx to be measured can be obtained——
- 4. As shown in the figure, if the line segments a and B are known and a > 3 / 2B, use a compass and a ruler to find a line segment X so that x = 2a-3b fast
- 5. It can be made up of four different numbers: 1, 2, 3 and 4______ Four digits without repetition
- 6. If the speed of the bicycle is always a, the speed of the car is always B. If b = a + 1, who will arrive first? Party A and Party B start from a to B at the same time. The way to take this part of the road is to ride a bicycle for the first two-thirds of the distance and take a car for the last one-third of the distance. Party B's way is to ride a bicycle for the first two-thirds of the time and take a car for the last one-third of the time. If the speed of the bicycle is always a and the speed of the car is always b, if B = a + 1, who will arrive first?
- 7. On a 1:6000000 map, the distance between Beijing and Shanghai is 17.5cm How many hours does it take for a car to go from Beijing to Shanghai at the speed of 84 kilometers per hour?
- 8. The distance between the two places is 270 kilometers. A and B cars leave from the two places at the same time. They meet in three hours. The speed ratio of a and B cars is 5:4, and the speed of the two cars is 5:4 The distance between the two places is 270 kilometers. A and B cars leave from the two places at the same time and meet each other in three hours. The speed ratio of a and B cars is 5:4. What's the speed of the two cars?
- 9. The number of male workers accounts for 60% of the total number, and the number of female workers is equal to ()
- 10. 5 / 8 of a is equal to 5 / 9 of B. A: B = (): ()
- 11. Let n-dimensional vector group A1, A2,..., as, as + 1 (s)
- 12. If E1 and E2 are a group of bases in the plane, then the following four groups of vectors can be used as bases of plane vectors A、e1-e2,e2-e1B、2e1-e2,e1-1/2e2C、2e2-3e1,6e1-4e2D、e1+e2,e1-e2
- 13. The equations X / 2-y + 1 / 3 = 1,3x + 2Y = 10
- 14. As shown in the figure, in the parallelogram ABCD, the diagonal lines AC and BD intersect at point O, and the straight lines passing through point O intersect AD and BC at points m and N respectively. If the area of △ con is 2 and the area of △ DOM is 4, then the area of △ AOB is 2______ ．
- 15. Known circle C: (x-1) ^ 2 + (Y-2) ^ 2, through the point P (2, - 1) as the tangent of circle C, the tangent points are a and B Known circle C: (x-1) ^ 2 + (Y-2) ^ 2 = 2, through the point P (2, - 1) as the tangent of circle C, the tangent points are a and B
- 16. The function f (x) = 1 / 2x ^ 2-alnx is known. When a = - 1, it is proved that the function f (x) increases monotonically on (0, + infinity). 2 find the extremum of F (x)
- 17. Is f (x) = - x + 2x + 1 x an increasing or decreasing function on [1, positive infinity]
- 18. Given the function f (x) = 2x / x2 + 1, we prove that it is a decreasing function in [1, positive infinity]
- 19. It is proved that f (x) = X-1 / X is an increasing function in the interval (0, positive infinity) It's x minus 1 / X. it's a detailed process. Thank you~~~
- 20. Given the function FX = - 3 / x, it is proved by definition that FX is an increasing function in the interval (negative infinity, 0)