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Electrical Resistance Electrothermal Science Paper
Release date:
03 Apr,2020
The greater the electrical resistance, the greater the heat generated
The English physicist Joule did a lot of experiments and in 1840 he determined the following law accurately for the first time:
The heat generated by an electric current through a conductor is proportional to the square of the current, proportional to the resistance of the conductor, and proportional to the time of energization. This law is called Joule's law. Can be expressed as: Q = I2Rt
In the formula, the unit of current I should be A, the unit of resistance R should be ω, the unit of general time t should be s, so the unit of heat Q should be J.
When the current passes through the conductor, if all the electrical energy is converted into internal energy, and not into other forms of energy at the same time, that is to say, the work done by the current is used to produce heat. Then the heat Q produced by the current is equal to the work W done by the current, i.e. Q=W=UIt, and according to Ohm's law U=IR, then Q=I2Rt. It can be seen that in the case that all the work done by the current is used to produce heat, Joule's law can be derived from the electric work formula and Ohm's law formula.
The electric heater is a heating device made by using the thermal effect of electric current, and its main component is the heating element. The heating element is made of an alloy wire with high resistivity and high melting point wrapped around the insulating material.
The same length and thickness of the resistance wire and copper wire, resistance wire resistance is greater. When the resistor wire and the copper wire are connected in series on the circuit, they have equal internal current. Gradually increasing the supply voltage increases the current inside the resistor and copper wire, at which point the foam comes into contact with the resistor wire. 2. The heat released by the resistor wire melts the foam and cuts it off. Then the foam is placed on the copper wire. Since the resistance of the copper wire is small, the heat released is also small, so the foam does not melt and cut. From the above phenomenon, it can be seen that the current in the resistive wire and the copper wire are equal. The conductor wire is more resistive and gives off more heat.
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04 Jan,2022
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