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In Resistance heating the method of heat control is
By change the number element
By changing tapping
By inserting with external resistance
All of the above
All of the above
Resistance heating control relies on regulating the heat produced by an electrical element, which is governed by Joule's Law of heating. By manipulating either the voltage across the element, the current flowing through it, or the physical configuration of the heating elements, the total heat output can be precisely varied to meet thermal requirements.
Resistance heating control relies on regulating the heat produced by an electrical element, which is governed by Joule's Law of heating. By manipulating either the voltage across the element, the current flowing through it, or the physical configuration of the heating elements, the total heat output can be precisely varied to meet thermal requirements.
H=I2Rt тАФ Heat produced in Joules
P=V2/R тАФ Power consumption based on voltage
The fundamental heat production in a resistor is given by H=I2Rt. To control H, we can change R (by adding external series resistance or changing the number of parallel/series elements), or change I (by using a transformer with tapping to vary the supply voltage).
Changing the number of elements allows for coarse adjustments in total resistance.
Transformer tapping provides a seamless way to vary voltage without dissipating power in external resistors.
External series resistance is simple but inefficient due to additional I2R losses.
Resistance heating is highly efficient for domestic appliances like toasters and water heaters.
High efficiency (nearly 100% conversion)
Clean and easy to control
No flue gases produced
Element oxidation at very high temperatures
Limited maximum temperature compared to arc heating
Industrial furnaces
Domestic heating appliances
Resistance welding
For high-power furnaces, transformer tapping is preferred over external resistors to avoid energy wastage.
Changing the number of elements is commonly achieved via series-parallel switching controls.
D is correct тАФ All listed methods (changing the number of elements, transformer tapping, and series resistance) are standard techniques used to regulate the heat output in resistance heating systems.
Always remember that inserting external resistance is an inefficient method for high-power industrial applications because it results in unnecessary I2R power loss.