SSC JE Electrical 2019 with solution SET-2
While estimating the overhead lines, if the number of poles required is 14, then what is the estimated number of earth sets required?
While estimating the overhead lines, the first and last pole is always earth connected and after every 3rd electrical pole, the fourth pole is earthed. Therefore, the approximate number of required ground set = 4
The amount of flux produced by the magnet indicates the strength of the magnet. The more the magnetizing force (MMF), the more is the flux produced. The more the opposition to the flux path (i.e., reluctance or magnetic resistance) less is the flux produced. This relationship is expressed as Flux = MMF/ Reluctance Reluctance is the opposition offered by the material in the flux path to the establishment of the flux. The reluctance in a magnetic circuit is similar to the resistance in an electric circuit. Reluctance is the inverse of permeance. MMF = Flux/Permeance
This type of motor is designed to operate with the start winding and it’s series capacitor permanently connected to the supply. lt has two capacitors connected in parallel in the start winding circuit for starting purposes. The running capacitor is employed to correct the power factor. As a result, this motor has a higher starting torque as well as a higher efficiency. These motors are employed in sizes ranging from 375 W to 7.5 kW. The power factor of these motor is upto 80% to 100%.
⇒ The electric potential at a point is defined as the work done in bringing the unit positive charge ( +1C) from infinity to that point. The work done is independent of the path taken. Its unit is Volt (V). ⇒ Potential Difference (pd or V) is a measure of the difference in charge between two points in a conductor. Its unit is Volt (V). ⇒ The difference in charge produced by the battery is stored in the battery as electrical potential energy and is called electromotive force (shortened to emf). Electromotive force is also measured in volts. Its unit is Volt (V). ⇒ Electric flux is a measure of how much the electric field vectors penetrate through a given surface. The SI unit of electric flux is N.m2/C. Electrical potential, Potential difference, Electromotive force has the same SI unit i.e Volt (V). Hence Electric flux is alike from others.
We use universal motors in mixer grinders. Universal motors can run both on a.c. and d.c. The universal motor works on the same principle that DC series motor works. DC series motor has the characteristics of operating at high-speed when there is no load and operating at low-speed when the load is applied. It has high starting torque characteristics. So it is used in mixers, where initially we put some load at starting.
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