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The length of the rectangle is 2xcm, the width is 4cm, the length of the trapezoid is xcm, the length of the bottom is 3 times of the length of the top, and the height is 5cm? How much bigger?
Rectangle area: 2x × 4 = 8xcm2, trapezoid area: 0.5 × (x + 3x) × 5 = 10xcm2, ∵ length: 2xcm, ∵ 10x > 8x, ∵ trapezoid area: 2xcm2, ∵ 10x-8x = 2xcm2, ∵ 2xcm2
For a trapezoid with a certain area, the length of the upper bottom is 13 times that of the lower bottom. Let the length of the upper bottom be xcm and the height be YCM, and when x = 5cm and y = 6cm, (1) find the functional relationship between Y and X; (2) find out the length of the lower bottom when y = 4cm?
(1) ∵ x = 5cm, y = 6cm, the length of the upper sole is 13 times that of the lower sole, the length of the lower sole is 15cm, the area of the trapezoid = 12 × (5 + 15) × 6 = 60, the height of the trapezoid = 2, the area of the trapezoid, the upper sole + the lower sole, y = 120x + 3x = 30x; (2) when y = 4cm, x = 7.5, 3x = 22.5
Why does the current in a metal conductor move in the opposite direction to the actual movement of free electrons?
Electric current is the opposite direction of the direction of the electron's directional movement. However, due to early mistakes in people's understanding, it was determined according to the law from positive to negative in nature. When we knew the truth, we did not change this law. The main reason is that this law conforms to the positive logic. If we use the direction of the electron flow, it becomes the negative logic
In a metal conductor, free electrons move in the opposite direction of the current
When an electron is negatively charged, the direction of current is a defined direction. The movement direction of negative and positive charge is opposite. The direction of current is defined as the direction of directional movement of positive charge. Because the free electron of metal conductor is negatively charged, the direction of actual directional movement of free electron of metal conductor is opposite to that of current
RELATED INFORMATIONS
- 1. Is the direction of current in a metal conductor opposite to that of free electrons?
- 2. If the current direction in the metal wire AB is from a to B, then the direction of the free electrons in the wire is from a to B___ To___ ．
- 3. Metal conduction refers to the directional movement of free electrons in the metal under voltage, but after the electrons in a power supply, a light bulb and a wire move Where does the electron go to the negative pole? Is there a new electron supplement or is the nucleus charged after the electron is removed
- 4. When the voltage applied at both ends of a resistor is 5V, the current passing through it is 0.5A. To make the current passing through the resistor 1a, add it to both ends of the resistor What is the voltage applied at both ends of the resistor? If the voltage at both ends increases to 20V, what is the resistance of the resistor? What is the current passing through it?
- 5. When the voltage applied at both ends of a resistor is 5V, the current passing through it is 0.5A. To make the current passing through the resistor 1a, add it to both ends of the resistor What is the voltage applied at both ends of the resistor? If the voltage at both ends increases to 20V, what is the resistance of the resistor? What is the current passing through it?
- 6. In the circuit shown, given resistance R1 = 4 Ω, R2 = 8 Ω, R3 = 6 Ω, R4 = 12 Ω, voltage US1 = 1.2V, US2 = 3V, use superposition theorem to calculate current I
- 7. Resistance R1 = 7 Ω, R2 = 5 Ω, connected in series at both ends of 12V power supply. At this time, the total resistance of the circuit is_____ Ω, R2 voltage___ 5. In parallel in a 3V circuit, The total resistance after parallel connection is____ Ω, when the current passes through the main road____ A. Comparison of current in R1 and R2____ . [a total of 5 blanks, yes, fill in the blanks = 3 =, no process, no matter]
- 8. When the voltage at both ends of a resistor increases from 3V to 4V, the current through it increases by 1a, and then the current in the conductor is? A
- 9. If 50V voltage is applied at both ends of the resistance, and 20c electric quantity of the resistance passes through the cross section within 10 seconds, the resistance value of the resistance is______ Ω．
- 10. In 5 minutes, if the electric quantity passing through the cross-sectional area of a conductor is 60C, the current passing through the conductor is 60C How much is it There are 20 identical lamps connected in series to a 200V circuit. The current at both ends of each lamp is A .4840V B.10V C.200V D.0.1V
- 11. In the middle of a cuboid with a length of 15cm, a width of 8cm and a height of 5cm, a round hole with a diameter of 6cm at the bottom is dug out. What is the surface area of the cuboid after digging out Please answer me quickly
- 12. If the height of the cone is 5cm, then the area of the bottom of the cylinder is () cm;
- 13. The length of a rectangle is 14.8cm. If you increase its length by 6.5cm and keep its width unchanged, the area will increase by 67.6cm2. What is the original area of this rectangle?
- 14. In parallelogram ABCD, BD is perpendicular to ad, ad = 6cm, the area of parallelogram is 24, find the length of BD and AC
- 15. The area of a parallelogram is 30cm & # 178;, and the area of a triangle with the same base and height is () CM & # 178
- 16. The three sides of a right triangle are 6cm, 8cm and 10cm respectively. What's the area of the triangle? What's the area of the bottom side of the triangle with a length of 10cm How many cm is the height?
- 17. The upper bottom of a trapezoid is 12.5cm. Reduce the lower bottom by 3.5cm and change it into a parallelogram. At this time, the area is reduced by 7cm. What is the area of the original trapezoid?
- 18. The cuboid with square cross section is 30cm long. If the length is increased by 5cm, the surface area will be increased by 80cm
- 19. A cuboid is obtained by heightening a cuboid by 2cm (the bottom remains unchanged), and the surface area of the cuboid is 40cm larger than that of the original cuboid;,
- 20. Pour water from a cold water with a bottom radius of 10 cm into an empty glass with a bottom radius of 5 cm and a height of 8 cm. When the glass is full, the water surface of the cold water cup will drop