The output power of a small hydropower station generator is 100kW, the output voltage is 500V, the resistance of the transmission line is 10 ohm, and the allowable power consumption is 4% of the output power, The output power of a small hydropower station is 100kW and the output voltage is 500V. The resistance of the transmission line is 10 ohm, the allowable power consumption is 4% of the output power, and the electricity consumption unit needs 220 V voltage. Ask: what are the turns ratio of primary and secondary coils of step-up transformer and step-down transformer

The resistance of the transmission line is 10 ohm, and the allowable power consumption is 4% of the output power. If the current of the transmission line is I2, there are 100kW * 0.04 = I2 ^ 2ri2 ^ 2 = 100000 * 0.04/20 = 400i2 = 20a, the output power of the generator is 100kW, the output voltage is 500V, so the original coil current is I1 = P1 / U1 = 100000 / 500 = 200A

How many liters of gasoline does a car need to travel 75 / 4 km when it runs 9 / 2 km and 9 / 25 l

9/25÷9/2×75/4
=3 / 2 (L)

There is a meter with internal resistance Rg = 2K ohm and full-scale current Ig = 40 microampere. If it is refitted into a 10mA ammeter, the parallel resistance should be calculated

If the measuring range is indicated by I and the parallel resistance is indicated by R, if not, there will be
(R//Rg)*I = Rg*Ig
(R*Rg/(R+Rg))*I = Rg*Ig
R = Rg*Ig/(I-Ig)
R = 2000*40*10^(-3)/(10-40*10^-3)
= 2000/249
≈8.03213 Ω

2-1-1-radical 2 is the absolute value

Analysis: the key to this problem is to remove the absolute value
Before removing the absolute value, we should distinguish the positive and negative of the polynomial in the absolute value
Due to 1

Electric energy exercises
How is the energy transformed in the following examples;
① Dad's electric razor is working_________
② Mother is ironing clothes with an electric iron_
③ My sister is doing the experiment of electrolyzing salt water
④ The newly installed energy-saving lamp is shining:_____

1. Conversion of electric energy into kinetic energy
2. Conversion of electric energy into heat energy
3. Conversion of electric energy into chemical energy
4. Conversion of electric energy into light energy and heat energy

What are the common sense of recycling life

1. Multi use of water: 70% of the earth's surface is covered with water, about 1.4 billion cubic meters of water, of which 96.5% is sea water. Although the rest is fresh water, more than half of it is ice, rivers and lakes, which can be directly used, accounting for only about 0.003% of the total water

If angle 1 + angle 2 is equal to 90 ° and angle 1 + angle 3 = 90 °, then the reason for angle 2 = angle 3 is

The remainder of the same angle is equal

M={x|x＞1} P={x|x²-6x+9=0}
Excuse me, that is the true subset of that. Why?

By solving the equation x & # 178; - 6x + 9 = 0, we get X1 = x2 = 3, so p = {3}, because 3 belongs to the set P and 3 belongs to the set M, so p is a subset of M and a proper subset, because M = {x | x ＞ 1}

In the circuit as shown in the figure, R1 and R2 are both constant value resistors, and the power supply voltage remains unchanged. When the switches S1 and S2 are closed, both meters have indication. If the switch S2 is opened, then ()
A. The indication of ammeter becomes larger and that of voltmeter becomes smaller B. the indication of ammeter becomes smaller and that of voltmeter becomes larger C. The indication of ammeter and voltmeter become smaller D. the indication of ammeter and voltmeter become larger

It can be seen from the figure that when the two switches are closed, the resistance R1 is short circuited, and there is only R2 in the circuit. The voltmeter measures the voltage at both ends of the resistance R2, that is, the power supply voltage U (because there is only resistance R2 in the circuit, so the voltage at both ends of the resistance R2 is the power supply voltage). The indication of the ammeter is: I = UR2; if the switch S2 is disconnected, the resistance

If the displacement is 6m in the second second second, then the acceleration is 6m_ M / S2, the displacement in the fifth second is_ m?

1. Since the displacement in the second second second is 6 meters, you should subtract the displacement in one second from the displacement in two seconds, that is, S2 -- S1 = (1 / 2) a (T2 ^ 2 -- T1 ^ 2) T1 = 1 T2 = 2 S2 -- S1 = 6, so a = 4
2.S5=(1/2)*4*5^2=50