(Nanguan Middle School, Rucheng County, Shandong Province, 274700). Example 1 An electric kettle has two heating wires. It is necessary to connect one of them to the power supply separately, and it takes 18 minutes to boil the water in the pot; it takes 36 minutes to separate the other pot on the same power source and boil the same pot of water. If two heating wires are connected in parallel and connected to the same power source, it takes minutes to boil the same pot of water; if two heating wires are connected in series and connected to the same power source, it takes minutes to boil the same pot of water.
Conventional solution: set the power supply voltage to U, the resistance of the two heating wires is the ruler 2, and the time required for each heating wire to be used separately is h and because in the four cases, the same pot of water is boiled, the current passes through the electric heating The heat generated by the wire 2, set the tangential length of PT to *O, PA = for example, let the radius of *0 be r, PAB be any secant intersection *0 at two points A, B, PCD is the cut of the center O Line, pay *0 at two points C and D.
Combining the above two points can be obtained: the total resistance of two electric heating wires connected in parallel without the circle is the total resistance of the two electric heating wires in series, and a fixed point is a straight line intersecting the circle, then the two lines connecting the intersection of the straight line and the circle The product is fixed. Furthermore, another way to prove the circular power theorem is obtained, and at the same time, our understanding of the connotation of the power theorem is deepened.
In the two concentric circles with O as the center, any point on the large circle is used as the secant of the small circle, and the product of the two line segments at the intersection of the secant and the small circle is a fixed value.
02, *3, ... intersect at two points A, B, at any point on the extension line of the line AB, the tangent to each circle, whether each cut point is on the same circle, why, the time required for the generation to solve z string = easy to see, the conventional solution process is complicated, the calculation is large, and it is easy to make mistakes. If you notice that the voltage between the conductors is constant and the heat generated by the current is equal, the relationship between the energization time and the conductor resistance can be simplified.
Because in the four cases, when the same pot of water is boiled, the heat Q generated by the current is equal, and the power supply voltage is not constant, the energization time is proportional to the electric wire resistance. Then, in a certain circuit in which the power supply voltage is constant, a temperature-adjustable electric heater is connected, and two electric heating wires having unequal resistance values ​​are inside the electric heater. When two heating wires are used in series, the electric power consumed by the electric heater is 220 watts; when only one electric heating wire with a large resistance value is used, the electric power consumed by the electric heater is 275 watts; if two electric heating wires are used in parallel , the electric power consumed by the electric heater is ().
The conventional solution of the tile: set the power supply voltage to L/, and the resistance of the two heating wires are respectively the ruler 2. When the two heating wires are used in series, the electricity consumed by the electric heater is only used when one of the electric wires with a large resistance value is used. The electric power consumed by the electric heater is 1+2 and the total resistance of the two electric heating wires is paralleled and the electric power consumed by the electric heater is Pu22+3 and is sorted into P; r. (1)).
Obviously, the above solution is more difficult. If you can flexibly use the relationship between electric power and resistance, the solution to this problem can be simplified.
Solution: It can be seen from P=g that when the voltage is constant, the electric power is inversely proportional to the resistance.
It is assumed that when only one electric heating wire with a small resistance value is used, the electric power consumed by the electric heater is P2. When the two electric heating wires are connected in series, the electric power consumption is consumed when the two electric heating wires are connected in parallel by the ruler string=foot 丨+. The electric power Pn = p1 + P2 is selected (D).
ASTM D2846 Water Supply Cpvc Fitting
Cpvc Union,Pressure Cpvc Tee,Pressure Cpvc Union,Astm Water Supply Cpvc Fitting
Zhejiang Huangyan Minghua Plastic Pipe Fitting CO.,LTD , https://www.pipefitting-mh.com