The heat developed in an electric iron is attributed to _______ power

Question

The heat developed in an electric iron is attributed to _______  power

Examoogle · Accepted Answer

True

Explanation: An electric iron acts as a purely resistive load, converting electrical energy into thermal energy via Joule's law. In AC circuits, the power that performs actual work or is dissipated as heat is defined as True Power (Active Power).

Working Principle: When current flows through the resistive heating element, electrons collide with the atoms of the conductor, resulting in the dissipation of energy as heat. Since the electric iron has a power factor of approximately unity ($cos\phi \approx 1$), the entirety of the power supplied is consumed as True Power ($P = VI$).

Key Formulas: $P = I^2 R$ — Joule's law of heating determining power dissipation; $P = V I \cos \phi$ — General formula for Active (True) power in AC circuits

Key Points: True power is the real power consumed by a load to perform useful work.; The electric iron is a resistive load, meaning the phase angle between voltage and current is zero.; Reactive power oscillates between source and load but does not contribute to net energy conversion in purely resistive elements.; Apparent power is the vector sum of True and Reactive powers, representing the total capacity required from the supply.

Advantages: Efficient conversion of electrical energy to thermal energy; High power factor operation

Disadvantages: High current draw can cause voltage drops in residential wiring; No energy storage capability (purely dissipative)

Applications: Domestic heating appliances; Incandescent lighting; Industrial resistive heating elements

Additional Info: In a purely resistive load, the power factor is 1, so the Apparent Power equals the True Power.. Reactive power (measured in VAR) exists only in inductive or capacitive loads where energy is stored in magnetic or electric fields.. Option B (Reactive) is incorrect as reactive power represents energy shuttled back and forth without doing net work.

Answer: C is correct — The heat developed in an electric iron is entirely due to True Power, which is the actual power dissipated as heat in the resistive heating element.

Exam Tip: Always remember that in any electrical circuit, heat is exclusively a product of True Power; reactive power components (inductors/capacitors) do not contribute to steady-state heat dissipation in an ideal circuit.

Related Questions

Discussion (0)