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Which of the following is a pure resistive device?
Transformer
Heater
Generator
Motor
Heater
A pure resistive device is one where the voltage and current are perfectly in phase, meaning the power factor is unity. A heater, typically using a nichrome heating element, converts electrical energy into thermal energy through pure ohmic resistance, unlike inductive or capacitive loads.
IS 302-2-30
A pure resistive device is one where the voltage and current are perfectly in phase, meaning the power factor is unity. A heater, typically using a nichrome heating element, converts electrical energy into thermal energy through pure ohmic resistance, unlike inductive or capacitive loads.
P=I2R тАФ Power dissipation in a resistor
V=I├ЧR тАФ Ohm's Law relationship
╧Х=0┬░ тАФ Phase angle in a purely resistive circuit
The principle relies on Joule's Law of heating, where the electric current encounters resistance in the material, resulting in the dissipation of energy as heat. Since the element is non-inductive and non-capacitive, it exhibits only ohmic resistance, keeping the phase difference between voltage and current equal to 0┬░.
Resistive devices have a Power Factor of 1.
Pure resistance causes no magnetic or electric field energy storage.
The instantaneous power in a resistive device is never negative.
High efficiency in conversion to thermal energy
Independent of frequency fluctuations
Limited to heating applications
Does not contribute to power factor correction
Electric iron
Water heater
Incandescent lamps
Transformers, generators, and motors are inductive loads containing coils that create magnetic fields, causing the current to lag behind the voltage.
A pure resistive load produces a voltage drop that is directly proportional to the current flow as defined by Ohm's Law.
B is correct тАФ The heater is a purely resistive device because its heating element has negligible inductance and capacitance, resulting in a unity power factor.
Always remember that any device containing windings (coils) will possess inductance, meaning it cannot be classified as purely resistive; look for heating elements when identifying resistive loads in competitive exams.
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