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Which application need smallest size of motor?
Table fan
Sewing machine
Domestic mixture
Electric clock
Electric clock
An electric clock requires a tiny power output (typically a fraction of a watt to a few watts) merely to drive the clock gear mechanism. Consequently, it uses the smallest motor among all the given options, typically a synchronous micro-motor or a hysteresis motor. In contrast, domestic mixers, sewing machines, and table fans require significantly higher power ratings (ranging from 30 W to over 750 W).
An electric clock requires a tiny power output (typically a fraction of a watt to a few watts) merely to drive the clock gear mechanism. Consequently, it uses the smallest motor among all the given options, typically a synchronous micro-motor or a hysteresis motor. In contrast, domestic mixers, sewing machines, and table fans require significantly higher power ratings (ranging from 30 W to over 750 W).
P=T├Ч╧Й тАФ Mechanical power requirement where T is torque and ╧Й is angular velocity
NsтАЛ=P120fтАЛ тАФ Synchronous speed equation governing electric clock timing motors
In an electric clock, a small single-phase synchronous or hysteresis motor rotates at a constant speed precisely synchronized with the supply frequency (f). The mechanical power output requirement is extremely low because it only needs to overcome the light frictional resistance of the gear train.
Electric clocks utilize micro-synchronous motors or hysteresis motors requiring minimal torque.
Motor size is directly proportional to its continuous power/torque rating and heat dissipation requirements.
Domestic mixers use universal motors rated between 500 W to 750 W to handle heavy mechanical loads.
Table fans usually use permanent split capacitor (PSC) or shaded-pole induction motors rated around 30 W to 100 W.
Extremely low power consumption
Compact physical footprint
Silent and maintenance-free operation
Extremely low torque capacity
Cannot drive heavy mechanical loads
Electric wall clocks and time-keepers
Timer mechanisms in household appliances
Chart recorders and signaling devices
Option A (Table Fan): Requires a motor rated around 30 W тАУ 100 W to drive fan blades against air resistance.
Option B (Sewing Machine): Requires a fractional horsepower motor (typically 50 W тАУ 100 W) to pierce fabrics.
Option C (Domestic Mixture): Uses high-power Universal Motors (500 W тАУ 750 W) running at high speeds (10,000 to 18,000 RPM).
D is correct тАФ Electric clocks require an extremely small power output (fraction of a watt), necessitating the smallest motor among the given applications.
In competitive exams, remember that motor frame size is dictated primarily by torque requirement (TтИЭVolume┬аof┬аMotor). Higher torque or higher power applications demand significantly larger physical motor dimensions.