By the term, torque is meant the turning or twisting moment of a force about an axis. It is measured by the product of the force and the radius at which this force acts. Consider a pulley of radius r meter acted upon by a circumferential force of F Newton which causes it to rotate at N r.p.m. The angular speed of the pulley is ω = 2πN/60 rad/sec Work is done by this force in one revolution = Force × distance = F × 2πR Joule The power developed = Work Done/Time = (F × 2πR)/60/N = (F × R) × (2πN)/60 The power developed = T × ω watt or P = T ω Watt pmech = (ωT)
The luminous efficiency of an electric lamp is the ratio of the luminous flux (in lumen) emitted by the lamp to the electric power (watt) given to it i.e. Luminous efficiency η = Luminous flux/Watt Note:- Lumens is the unit of measurement for luminous flux, which is the total amount of visible light emitted by a source. 1
The average value of the sine wave over one complete cycle is actually zero. Hence, for a sine wave, the average value is defined over half the period. The average value expressed in terms of peak value is given by Average value = 0.637 × peak value
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