The formula for calculating current, voltage and resistance,

The formula for calculating current, voltage and resistance,

According to Ohm's Law: I = u / R, where: I - current (a); U - voltage (V); R - resistance (Ω)
How can heat energy be directly converted into electricity!?
According to the thermoelectric effect can be achieved (1834 French physicist Peltier connected a bismuth wire to each end of the copper wire. After connecting the two bismuth wires to the positive and negative poles of the DC power supply respectively, after power on, it was found that one joint became hot and the other joint became cold
How to convert electric energy into heat energy
Macroscopic: Joule's law q = I & # 178; RT
Conductor current is the directional action of electrons. Electrons move to collide with atoms. A large number of collisions aggravate atomic motion and increase internal energy
Through resistance q = I2R
Electric energy is transformed into kinetic energy by electromagnetic induction, and then into heat energy by kinetic energy
Through the resistance, the resistance heats up
This is the principle of electric heating
Heat energy is essentially the kinetic energy of microscopic particles. When the "cold" electrons in a material are accelerated under the action of an external electric field, they become "hot" electrons. A large number of such "hot" electrons gather together. A macroscopic manifestation is that the temperature rises, and the so-called electric energy is converted into thermal energy
Direct conversion of heat energy into electricity
It's the conversion of heat energy from an object at room temperature into electricity
The basic principle of thermocouple is to weld two conductors or semiconductors A and B of different materials together to form a closed loop. When there is a temperature difference between the two contact points 1 and 2 of conductor a and B, electromotive force will be generated between them, thus forming a
Copper weighs 9.8 kilograms per cubic meter
30x8.9 = 267kg
It's not right upstairs, is it
The formula of base area of cylinder
What is the base area of the cylinder?
It's the area of a circle
Π r squared
47) if the EMF of the power supply is 6V, the internal resistance is 1 ohm, and the resistance of the external circuit is 11 ohm, the output power of the power supply is 0
I = E / R total = 6 / 12 = 0.5A
P = I ^ 2 * r = 0.5 ^ 2 * 11 = 2.75w
11 times 0.25 w
There is an electric heater marked with "220 V, 40 Ω". With this electric heater, the water with a mass of 2 kg and an initial temperature of 20 ℃ can be boiled under the rated voltage. If the efficiency of the electric heater is 50%, how long will it take?
Heat absorbed by water: & nbsp; & nbsp; q = cm (t-t0) = 4.2 × 103J / (kg ·℃) × 2kg × (100 ℃ - 20 ℃) = 6.72 × 105J; according to Joule's Law: η u2rt = q, then t = QR, η U2 = 6.72 × 105 × 400.5 × 2202s = 1110.7s A: it takes 1110.7s
A rectangular copper bar weighs 18000 grams. Its length is 2 meters, and its cross section is a square with a side length of 3cm. How many kilograms does copper weigh per cubic decimeter? What is the volume of 7.2 tons of such a copper bar
A cuboid copper bar weighs 18000g, that is, 18kg. Its length is 2m, that is, 20decim, and its cross section is a square with a side length of 3cm (that is, 0.3dm). Its volume is 1.8cubic decimeter, so the copper weight of each cubic decimeter is 10kg
7.2 tons (7200 kg) of this copper rod, the volume is 720 cubic meters
18kg/(20*0.3*0.3)=10kg
7200kg/10kg=720dm^3
9.8 for junior high school students.
Area formula of cylinder
Cut a cylinder with a bottom radius of 5cm and a height of 18cm into two and a half cylinders along the bottom diameter, and find out how many square centimeters the surface area will increase?
5 × 2 = 10cm, 10 × 18 = 180cm, 180 × 2 = 360CM A: the surface area is increased by 360 cm. In fact, the surface area of this question only increases the two rectangles in the middle after cutting. The diameter of the cylinder is equal to the width of the rectangle, and the height of the cylinder is equal to the length of the rectangle