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What type of heating has the leading power factor
Induction heating.
Resistance heating.
Dielectric heating.
Electric arc heating.
Dielectric heating.
Dielectric heating involves placing a non-conductive material (dielectric) between two electrodes connected to a high-frequency AC supply. Because the dielectric behaves like a capacitor, the current leads the voltage by nearly 90 degrees, resulting in a leading power factor.
Dielectric heating involves placing a non-conductive material (dielectric) between two electrodes connected to a high-frequency AC supply. Because the dielectric behaves like a capacitor, the current leads the voltage by nearly 90 degrees, resulting in a leading power factor.
P=2πfCV2tan(δ) — power dissipated in dielectric heating
cos(ϕ)=sin(δ)≈δ — power factor of the dielectric load
When a high-frequency voltage is applied across a dielectric material, the dipoles within the material undergo continuous reorientation. This molecular friction generates heat. Electrically, the arrangement acts as a leaky capacitor with high capacitive reactance, causing the leading phase relationship between current and voltage.
Dielectric heating is used for materials with low electrical conductivity like wood, plastic, and food.
The power factor is leading because the load is essentially capacitive.
Higher frequency is required to increase heat generation.
The dielectric loss angle δ is very small, leading to a very low power factor.
Uniform heating throughout the material
Very rapid heating process
Easy control of temperature
No external heating elements required
High initial cost of equipment
Limited to non-conductive materials
Potential for interference with radio communications
Low efficiency for very thin materials
Gluing of wood
Preheating of plastic preforms
Drying of textiles and paper
Food processing (e.g., defrosting)
Induction heating uses electromagnetic induction on conductive materials, which results in a lagging power factor due to the inductive nature of the work coil.
Resistance heating is purely resistive with a unity power factor.
Electric arc heating is typically inductive due to the reactor/ballast used to stabilize the arc, resulting in a lagging power factor.
C is correct — Dielectric heating functions as a capacitive load, causing the current to lead the voltage and thus producing a leading power factor.
Always remember: Dielectric = Capacitor (Leading PF), Induction = Inductor (Lagging PF), Resistance = Resistor (Unity PF). This mapping solves most power factor questions in heating.