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)
Faraday’s 1st laws of electromagnetic induction tell us about the condition under which an e.m.f. is induced in a conductor or coil a when the magnetic flux linking a conductor or coil changes. Faraday’s 2nd laws of electromagnetic induction give the magnitude of the induced e.m.f in a conductor or coil and may be stated as: The magnitude of the e.mf induced in a conductor or coil is directly proportional to the rate of change of magnetic flux linkages. Suppose a coil has N turns and magnetic flux linking the coil increases (i.e. changes) from φ1 Wb to φ2 Wb in t seconds. Now, magnetic flux linkages mean the product of magnetic flux and the number of turns of the coil. N = e dφ/dt Lenz Law:- Lenz’s law states: the direction of the induced e.m.f. is such as to oppose the change producing it. Therefore, the magnitude and direction of induced e.m.f. should be written as : N = −e dφ/dt
Galvanized steel conductors do not corrode, and possess high resistance. Hence such Wires are used in telecommunications circuits, earth wires, guard wire, stray wire, etc.
EXAMIANS
