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Which one of the following is not the cause when the automatic electric iron does not heat properly?
Supply voltage is less
Setting of thermostat are not proper
Heating element is open circuited
Connection are loose
Heating element is open circuited
An 'open circuit' in the heating element means the electrical path is broken; consequently, no current can flow, and the appliance will not heat at all, rather than merely heating 'poorly'. Improper voltage, thermostat settings, or loose connections typically lead to intermittent or inefficient heating performance, whereas an open circuit causes a complete failure of the heating function.
An 'open circuit' in the heating element means the electrical path is broken; consequently, no current can flow, and the appliance will not heat at all, rather than merely heating 'poorly'. Improper voltage, thermostat settings, or loose connections typically lead to intermittent or inefficient heating performance, whereas an open circuit causes a complete failure of the heating function.
H=I2Rt тАФ Joule's Law of heating where H is heat, I is current, R is resistance, and t is time.
P=RV2тАЛ тАФ Power dissipation in the heating element relative to supply voltage V and resistance R.
The heating element operates based on Joule heating where H=I2Rt. If the circuit is open (infinite resistance), the current I becomes zero, resulting in zero heat production. Poor heating, on the other hand, is usually a symptom of increased series resistance (loose contacts) or reduced supply voltage which limits the power delivered to the heating element.
An open-circuited element results in zero current, meaning no heating occurs.
Loose connections create additional resistance at joints, leading to voltage drops and reduced heating.
The thermostat controls the average temperature; incorrect settings lead to improper cutoff or activation timing.
Low supply voltage reduces the power output as power is proportional to the square of the voltage (PтИЭV2).
Domestic electric iron maintenance
Troubleshooting industrial heating appliances
A faulty thermostat (e.g., contacts stuck open) is a common cause for no heating, similar to an open element.
Option A, B, and D describe scenarios where the iron receives power but functions inefficiently (poorly).
An open circuit is a binary state; it is either functional or failed, making it the 'odd one out' in the context of 'poor' heating.
C is correct тАФ Heating element open-circuiting causes a complete cessation of heating, not merely improper heating performance.
In competitive exams, always distinguish between 'No functionality' (open circuit, blown fuse) and 'Reduced performance' (low voltage, loose contact, improper thermostat calibration).