How much electric energy is converted into heat energy
at present, the most common way to convert electric energy into heat energy is to use electric heater.
Electricity can be converted into heat
Joule's Law: q = I & # 178; RT can be seen that electrical energy into heat and resistance are inextricably linkedcarriers (electrons for metals, anions and cations in solution...) move in a directional direction under the action of electric field force. Take the metal for example, the electrons make directional motion under the action of electric field force, but because the metal has temperature, the electrons have kinetic energy, they are doing disorderly thermal motion and colliding with each other
When the electric field force is added, the thermal motion of the collision will not be changed, and the collision will generate heat! In addition, metal atoms can also affect the movement of electrons, and metal atoms may be ionized by electron collision After that, this or another electron is captured because of the attraction of the nucleus, which is in dynamic equilibrium in the capture ionization process. The capture of this process will emit electromagnetic waves, most of which are visible light, and most of them are red and yellow, which is also the luminous principle of incandescent lamps Joule's law is a law that quantitatively explains that conction current converts electric energy into heat energy. In 1841, the British physicist Joule found that the heat Q (called Joule heat) generated in the current carrying conctor is proportional to the square of current I, the resistance R of the conctor and the power on time T. This Law is called Joule's law The international system of units (SI) is adopted, and its expression is q = I & # 178; RT or thermal power P = I & # 178; The units of Q, I, R, t and P are Joule (J), ampere (a) and ohm Ω)、 Second (s) and watt (W). The application of Joule's law in the series circuit: in the series circuit, the current is equal, the greater the resistance, the more heat generated. The application of Joule's law in parallel circuit: in parallel circuit, the voltage is equal, through the deformation formula, w = q = Pt = U2 / RT When u is constant, the larger R is, the smaller q is. It should be noted that Joule's law and electric work formula w = uit are only applicable to pure resistance circuits, that is, q = w = uit = I & # 178 can only be used in circuits such as electric heaters; Rt=U² t/RElectric energy is converted into heat energy, and one kilowatt hour (1kwh) energy is converted into 859.845 kcal
The solution process is as follows:1 card 20 ℃ = 4.1868j. 1 kcal = 1000 kcal, mostly used in nutrition measurement and fitness manual
1 kwh = 1 kW × 1 hour = 1000 watts × 1 hour = 1000 watts × 3600 seconds = 3600000 joules
i.e. 1 kwh = 3.6 × 10 ^ 6 joules
3.6 × 10^6 ÷ 4.1868=859 845 eight hundred and fifty-nine thousand eight hundred and forty-five ÷ 1000 = 859.845 kcal
extended data:
when the temperature of 1kg pure water increases or decreases by 1 ℃, the heat absorbed or released is 1 kcal. A large calorie is a kilocalorie. It is used to evaluate the quality of fuel. One kilogram of fuel can make x kilogram of water increase by 1 degree Celsius, which means that the calorific value of this fuel is x kcal
1 kcal / kg = 1 kcal / kg = 4.1868 kJ = 1 kcal / gits relationship with Joule is: 1 kcal 20 ℃ = 4.1868j
some countries use 15 ℃ kcal. The relationship between it and Joule is: 1 card 15 ℃ = 4.1855j
some countries use international steam meter card it. The relationship between it and Joule is: 1 card it = 4.1868j
1. The current directly passes through the resistance wire, and the resistance wire generates heat. Such as electric furnace, electric water heater, incandescent lamp, etc
2. Electromagnetic inction proces heat. For example, in inction cooker, the current and voltage are converted into direct current through rectifier, and then the direct current is converted into high-frequency alternating current beyond audio frequency through high-frequency power conversion device, and the high-frequency alternating current is added to the flat hollow spiral inction heating coil to generate high-frequency alternating magnetic field. The magnetic line of force penetrates the ceramic plate of the stove and acts on the metal pot. In the cooking pot, there is a strong eddy current e to electromagnetic inction. When the eddy current overcomes the internal resistance of the pot body, it completes the conversion of electric energy to heat energy, and the Joule heat generated is the heat source of cooking
3. The microwave is converted into heat, and the magnetron converts the electric energy into microwave, which is fed into the microwave cavity by the waveguide. As long as the things in the microwave cavity are composed of "polar molecules", they can absorb the microwave and convert the microwave into the internal heat of the object.
Q=I² RT, Joule's law is a quantitative description of the conction current to convert electrical energy into heat
the content is: the heat generated by the current passing through the conctor is proportional to the second power of the current, to the resistance of the conctor, and to the power on time. Mathematical expression of Joule's Law: q = I & # 178; Rt For pure resistance circuit, we can dece that q = w = Pt; Q=UIt; Q=(U²/ R)t
Joule's law is an experimental law, which can be applied to any conctor and can be used in all circuits. When encountering the problem of current thermal effect, for example, to calculate the heat released when the current passes through a circuit; Joule's law can be used to compare the amount of heat released by a certain section of circuit or conctor, that is, to consider the requirements of the circuit from the perspective of current thermal effect
extended data:
it should be noted that w = (u ^ 2 / R) t is derived from Ohm's law, which can only be established under the condition that the work done by the current converts all electric energy into heat energy (pure resistance circuit). For example, for electric appliances such as electric furnaces and electric soldering irons, the two formulas and Joule's law are equivalent
when Joule's law formula is used for calculation, the physical quantities in the formula should correspond to the same conctor or the same section of circuit, which is the same as Ohm's law. When several physical quantities appear in the title, they should be added with corner code to show the difference
note: w = Pt = uit is suitable for all circuits, while w = I & # 178; RT = (u ^ 2 / R) t is only used in pure resistance circuit (all used for heating)