If B is the flux density, I the length of conductor and v the velocity of conductor, then induced e.m.f. is given by Blv.
In an induction motor if the flux density is reduced to one-half, of its normal value then the torque will (1) reduce to one-half (2) reduce to one-fourth (3) remain unchanged (4) increase four times
Last Answer : In an induction motor if the flux density is reduced.to one-half, of its normal value then the torque will reduce to one-fourth
Last Answer : When the armature of a D.C. motor rotates, e.m.f. induced is back e.m.f.
Flux density formula
Last Answer : Flux density formula
Define the following terms: i) Magnetic flux density, ii) Reluctance, iii) Magneto-motive force, iv) Permeance.
Last Answer : (i) Magnetic flux density (B): It is the magnetic flux per unit area measured at right angles to the flux path. (Its unit is weber/m2 or tesla). (ii) Reluctance: It is the ... flux to set up through it and it is reciprocal of reluctance. Permeance = 1/ Reluctance. Unit: weber/ampere.
Give the relation between magnetic field strength, magnetic flux density and permeability.
Define magnetic flux density and state its formula.
Last Answer : The magnetic flux per unit area is called as magnetic flux density. Magnetic flux density is denoted by B. The formula for magnetic flux density is Weber per metre square or Tesla. Mathematically ... the unit of magnetic flux density is Weber per metre square which is also called as Tesla.
What is the permissible flux density in case of cold rolled grained oriented steel?
Last Answer : The permissible flux density in case of cold rolled grained oriented steel is 1.7 Wb/m2.
Last Answer : Flux density is denoted by B. And it is given as B = flux/ area Where, the unit of flux is Weber and unit of area is meter square. So the unit of flux density is weber per meter square which is also called as Tesla.
Explain dynamic and static induced emf with neat diagram.
Last Answer : Dynamically Induced EMF:- In this case, either coil moves or magnet moves, so that there is relative motion between coil & magnetic field. Thus magnetic field is cut by coil & emf is induced in it. The emf ... The expression for induced EMF is e= -L(di/dt) or = -N(dϕ/dt).
Self induced emf and Mutually induced emf
Last Answer : (i) Self-induced e.m.f.: The e.m.f. induced in a coil due to the change of its own flux linked with it, is called self-induced e.m.f. (ii) Mutually induced e.m.f.: The e.m.f. induced in a coil due to the changing current in the neighbouring coil, is called mutually induced e.m.f.
Compare statically induced emf with dynamically induced emf on any four points.
Last Answer : Statically induced emf Dynamically induced emf Emf is induced without any relative motion between conductor and magnetic field. Emf is induced due to relative motion between conductor ... induced in transformer windings e.g emf induced in Generator, Alternator armature windings
Explain the term self induced EMF with a neat diagram.
Define: 1) statically induced EMF 2) dynamically induced EMF Write the names of equipments in which these two types of EMF get induced
Last Answer : Concept of statically induced emf: The emf induced in coil or conductors without any relative motion between it and magnetic field is called statically induced emf. When conductor is stationary and flux ... it. This emf is dynamically induced emf. e.g. Emf induced in generators, alternator.
List the two types of induced EMF.
Last Answer : There are two types of EMF one is statically induced EMF and second is dynamically induced EMF.
The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors rotating at 600 rpm and with 1 Wb flux per pole is (1) 1000V (2) 100V (3) 600V (4) 10,000V
Last Answer : The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors rotating at 600 rpm and with 1 Wb flux per pole is 1000V
Last Answer : Interpole flux should be sufficient to neutralise both the armature reaction flux as well as commutating e.m.f. induced in the coil.
An energy signal has G(f) = 20. Its energy density spectrum is A) 20 B) 100 C) 400 D) 800
Last Answer : 400
Current velocity through a copper conductor is
If a wire conductor of 0.2 ohm resistance is doubled in length, its resistance becomes?
Last Answer : If a wire conductor of 0.2 ohm resistance is doubled in length, its resistance becomes 0.4 ohm.
Self induced voltage across an inductance
Last Answer : Self induced voltage across an inductance
Faraday's law of induced voltage
Last Answer : Faraday's law of induced voltage
Define natural, mechanical, forced and induced draught systems.
Last Answer : Natural draught system: - When the fuel is burnt (combustion) in the furnace due to natural circulation of air, the draught is called natural draught. Mechanical draught system: - In a mechanical ... combustion. OR If fan/blower is placed after the furnace then it is called as induced draught
How can we increase the induced current?
Last Answer : Induced current can be increased by reducing no of windings on the secondary part compared to primary.
What is the direction of the induced electric field?
Last Answer : It is in opposite direction to the one that produced it.
What is the direction of the induced current?
A straight wire of length 0.20 m moves at a steady speed of 3.0 m s-1 at right angles to the magnetic field of flux density 0.10 T. The e.m.f induced across ends of wire is A. 0.5 V B. 0.06 V C. 0.05 V D. 0.04 V
Last Answer : 0.06 V
In lead acid battery the density of acid indicates the (1) charge of the battery (2) level of acid (3) e.m.f of the battery (4) damage of the plates
Last Answer : In lead acid battery the density of acid indicates the charge of the battery
Define the following terms and state their units: (i) Luminous intensity, (ii) Luminous flux
Last Answer : i) Luminous intensity: This is defined as the luminous flux emitted into a solid angle of space in a specific direction. Its unit is the candela. OR The luminous flux per unit solid angle ( ... energy radiated by the light source in all direction. The unit of luminous flux is lumen (lm)
Describe the concept of leakage flux, useful flux and fringing with neat diagram.
Last Answer : Leakage Flux
Define useful flux, leakage flux and fringing.
Explain the leakage flux and its effect with the help of neat diagram.
In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation, the machine is operating as (1) synchronous motor (2) synchronous generator (3) asynchronous motor (4) asynchronous generator
Last Answer : In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation, the machine is operating as synchronous generator
Which of the following is a unit of magnetic flux? A) Weber B) Maxwell C) Both A and B D) None of these
Last Answer : Which of the following is a unit of magnetic flux? A) Weber B) Maxwell C) Both A and B D) None of these
It is possible to increase the field flux and, at the same time, increase the speed of a d.c. motor provided its .......... is held constant.
Last Answer : It is possible to increase the field flux and, at the same time, increase the speed of a d.c. motor provided its armature current is held constant.
The property of a material which opposes the creation of magnetic flux in it is known as?
Last Answer : The property of a material which opposes the creation of magnetic flux in it is known as reluctance.
The unit of magnetic flux is?
Last Answer : The unit of magnetic flux is weber.
The path of magnetic flux in a transformer should have?
Last Answer : The path of magnetic flux in a transformer should have low reluctance.
The counter e.m.f. of a d.c. motor?
Last Answer : The counter e.m.f. of a d.c. motor helps in energy conversion.
Last Answer : E.m.f. of a Weston cell is accurately measured by electrostatic voltmeter.
Last Answer : It is required to measure the true open circuit e.m.f. of a battery. The best device is D.C. potentiometer.
Last Answer : The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is 0.5.
Last Answer : In case of D.C. shunt motors the speed is dependent on back e.m.f. only because flux is practically constant in D:C. shunt motors.
Last Answer : The armature may burn if the back e.m.f. of a D.C. motor vanishes suddenly.
Explain the suitability of aluminium as an electrical conductor with respect to its mechanical and electrical properties.
Last Answer : Following are requirements of conductor:- i) High conductivity : Material should have high conductivity, So that * cross section of conductor (size) reduces, * Copper losses reduces, * So Efficiency ... . Boiling point is 1820°C 9. Specific gravity is 2.7 10. High resistance to corrosion.
State properties of conductor material used for overhead conductor.
Last Answer : Following are the properties of conductor material:- 1. High conductivity :- Material should have high conductivity 2. High mechanical strength:- Material should have sufficiently high mechanical strength ... available & less costly. 9. Scrap Value: - Material should have high scrap value.
Last Answer : Which allows the flow electrons
reasons the transposition of conductor
Last Answer : Following reasons the transposition of conductor: 1. Due transposition of conductor inductance of each line is same LA = LB = LC, So drop due to inductive reactance in each line is same so ... interferences are less due to transposition. Figure of transposition of conductor:
What is difference between Conductor and insulator ?
Last Answer : Conductor is a material that offers no resistance to the flow of current, while an insulator is a material that offers total resistance to the flows of current, It doesn't allowed any flows of current.
What is the difference between a cable and a conductor?