What is electro-motive force (emf) or voltage?

What is electro-motive force (emf) or voltage?
by

1 Answer

Answer :

It is the pressure that moves the electrons to flow in any conductor. It is also known as electromotive force voltage. Its symbol is ‘E’ or ‘V’ and measuring unit is volt measured by voltmeter. 
by

Related questions

What are the types of induced electro motive force?

Description : What are the types of induced electro motive force? 

Last Answer : a. Dynamically induced emf. b. Statically induced emf. Statically induced emf can be further divided into two groups. a. Mutually induced emf. b. Self induced emf. 

What is called the EIectro-Motive Force (EMF) of a voltage source?

Description : What is called the EIectro-Motive Force (EMF) of a voltage source? (1) Terminal voltage when load is applied (2) Internal voltage when no load is applied (3) Product of internal resistance and load current (4) Electric pressure provided to the load

Last Answer : What is called the EIectro-Motive Force (EMF) of a voltage source? (1) Terminal voltage when load is applied (2) Internal voltage when no load is applied (3) Product of internal resistance and load current (4) Electric pressure provided to the load

Find the force experienced by an electromagnetic wave in a conductor? a) Electrostatic force b) Magneto static force c) Electro motive force d) Lorentz force

Description : Find the force experienced by an electromagnetic wave in a conductor? a) Electrostatic force b) Magneto static force c) Electro motive force d) Lorentz force

Last Answer : d) Lorentz force

What is magneto motive force?

Description : What is magneto motive force?  

Last Answer : The force, which drives the magnetic flux through a magnetic circuit, is called the magneto motive force. 

Is there a test to prove that an EMF (electro-magnetic field) has damaged human body?

Description : Is there a test to prove that an EMF (electro-magnetic field) has damaged human body?

Last Answer : So you believe that EMF radiation does physiologic damage to the human body? If so, what makes you think this?

In the illustration, the diode between terminals 16 and 17 is to _________. EL-0046 A. insure that the voltage across the governor coil (EG-3P) never exceeds .6 VDC B. compensate for the temperature difference of the governor oil heating up C. protect the electronic governor from counter EMF D. act as a filter to prevent hunting

Description : In the illustration, the diode between terminals 16 and 17 is to _________. EL-0046 A. insure that the voltage across the governor coil (EG-3P) never exceeds .6 VDC B. compensate for the ... heating up C. protect the electronic governor from counter EMF D. act as a filter to prevent hunting

Last Answer : Answer: C

What are the advantages and disadvantages of estimating the voltage regulation of an Alternator by EMF method?

Description : What are the advantages and disadvantages of estimating the voltage regulation of an Alternator by EMF method?

Last Answer : Advantages: · Simple no load tests (for obtaining OCC and SCC) are to be conducted · Calculation procedure is much simpler Disadvantages: · The value of voltage regulation obtained by this method is always higher than the actual value

Define the following terms: i) Magnetic flux density, ii) Reluctance, iii) Magneto-motive force, iv) Permeance.

Description : 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.

The magneto-motive force is

Last Answer : The magneto-motive force is the sum of all currents embraced by one line of magnetic field.

Electro-mechanical voltage regulators are generally used in (a) reactors (b) generators (c) transformers (d) all of the above

Description : Electro-mechanical voltage regulators are generally used in (a) reactors (b) generators (c) transformers (d) all of the above

Last Answer : (b) generators

What are different types of principles of operation of electro-mechanical relays?

Description : What are different types of principles of operation of electro-mechanical relays?

Last Answer : Answer: Electro-mechanical relays operate by two principles. Electro-magnetic attraction and electromagnetic induction. In electromagnetic attraction relay plunger is drawn to the solenoid or an ... operation is similar to induction motor. Torque is developed by electromagnetic induction principle

What is meant by electro negativity of SF6 gas?

Description : What is meant by electro negativity of SF6 gas?

Last Answer : SF6 has high affinity for electrons. When a free electron comes and collides with a neutral gas molecule, the electron is absorbed by the neutral gas molecule and negative ion is formed. This is called as electro negativity of SF6 gas.

State the faraday’s laws of electro magnetic induction.

Description : State the faraday’s laws of electro magnetic induction.

Last Answer : In 1831 Faraday discovered the production of electric current in electric conductor by converting magnetism. Faraday has mentioned two laws known as faraday's laws of electro magnetic induction. First ... conductor is directly proportional to the rate of change of flux linked with that conductor. 

Who discovered electro magnetism?

Description : Who discovered electro magnetism?

Last Answer : ‘Orsted’ a denish scientist discovered that whenever an electric current passes through a conductor, a magnetic field will be produced around that conductor in concentric circle. In addition to that heat will be produced in that conductor.  

What are the advantages of electro magnetism?

Description : What are the advantages of electro magnetism? 

Last Answer : a. Electro magnets can be magnetised very easily by sending DC through it. b. Changing the direction of the current through the coil can change the polarity of the poles. c. The strength of ... depending upon the need. e. The magnetic strength remains constant as long as the current is constant.

What is electro plating?

Description : What is electro plating?

Last Answer : The process of depositing a metal on the surface of another metal by electrolysis is known as electro plating. Usually the plating material will be silver, chromium etc. 

How does voltage drop related to impressed emf?

Description : How does voltage drop related to impressed emf?

Last Answer : Voltage drop is resultant of IR ie current and the lineresistance, not dependent on impressed emf

What term describes voltage or emf?

Description : What term describes voltage or emf?

Last Answer : Difference of potential.

The terminal voltage of a cell supplying energy to a circuit is usually less than its emf because of the cell's w) size x) internal resistance y) mass z) energy

Description : The terminal voltage of a cell supplying energy to a circuit is usually less than its emf because of the cell's w) size x) internal resistance y) mass z) energy

Last Answer : ANSWER: X -- INTERNAL RESISTANCE

Why the emf of a cell is always greater than its terminal voltage? Explain the same.

Description : Why the emf of a cell is always greater than its terminal voltage? Explain the same.

Last Answer : Every practical source offers some opposition to the current due to its internal parts or components. Such a resistance of internal parts of source is called internal resistance of source. When source delivers ... less than emf induced. So, emf of a cell is always greater than terminal voltage.

The emf of a primary cell depends upon the: a) Physical dimension of the cell b) Nature of the electrolyte c) Nature of the electrode d) Both (b) and (c)

Description : The emf of a primary cell depends upon the: a) Physical dimension of the cell b) Nature of the electrolyte c) Nature of the electrode d) Both (b) and (c)

Last Answer : Ans: D

The electrical schematic illustrated in figure A, depicts a/an _____________. EL-0059 A. autotransformer B. Delta Wye transformer C. primary EMF generator D. potential transformer

Description : The electrical schematic illustrated in figure A, depicts a/an _____________. EL-0059 A. autotransformer B. Delta Wye transformer C. primary EMF generator D. potential transformer

Last Answer : Answer: D

Which of the following statements describes what will occur if the motor shown in the illustration is required to carry 150% of full load? EL-0056 A. The primary counter emf will be increased. B. The stator current will increase. C. The slip will decrease. D. The slip value, stator current curve, and torque curve will all coincide.

Description : Which of the following statements describes what will occur if the motor shown in the illustration is required to carry 150% of full load? EL-0056 A. The primary counter emf will be increased. B. ... slip will decrease. D. The slip value, stator current curve, and torque curve will all coincide.

Last Answer : Answer: B

An increase in the amount of current flow through the armature of a shunt motor is the final result of a/an _____________. A. increase in the load on the motor B. decrease in the load on the motor C. increase in counter EMF D. decrease in armature torque

Description : An increase in the amount of current flow through the armature of a shunt motor is the final result of a/an _____________. A. increase in the load on the motor B. decrease in the load on the motor C. increase in counter EMF D. decrease in armature torque

Last Answer : Answer: A

The counter EMF of a DC motor is maximum when the _________. A. motor is at rated speed B. armature is not turning C. motor is almost up to rated speed D. armature has just begun to turn

Description : The counter EMF of a DC motor is maximum when the _________. A. motor is at rated speed B. armature is not turning C. motor is almost up to rated speed D. armature has just begun to turn

Last Answer : Answer: A

The counter EMF produced in the windings of a DC motor is 'zero' when the ____________. A. armature has just begun to turn B. armature is not turning C. motor is almost up to rated speed D. motor is at rated speed

Description : The counter EMF produced in the windings of a DC motor is 'zero' when the ____________. A. armature has just begun to turn B. armature is not turning C. motor is almost up to rated speed D. motor is at rated speed

Last Answer : Answer: B

Which of the following types of DC motors has its field connected in parallel with its armature? A. Counter EMF B. Shunt C. Salient pole D. Series

Description : Which of the following types of DC motors has its field connected in parallel with its armature? A. Counter EMF B. Shunt C. Salient pole D. Series

Last Answer : Answer: B

The ratio of the effective value of the counter EMF in volts, to the effective value of the current in amperes is called _____________. A. impedance factor B. capacitive reactance C. inductive reactance D. root mean square

Description : The ratio of the effective value of the counter EMF in volts, to the effective value of the current in amperes is called _____________. A. impedance factor B. capacitive reactance C. inductive reactance D. root mean square

Last Answer : Answer: C

The unit of apparent power in a purely inductive circuit is called the _____________. A. kva B. var C. emf D. watt

Description : The unit of apparent power in a purely inductive circuit is called the _____________. A. kva B. var C. emf D. watt

Last Answer : Answer: B

EMF equation of the transformer?

Description : EMF equation of the transformer?

Last Answer : A. E = 4.44ΦmfN Volts. If E1 & E2 are primary and secondary emf’s and N1 & N2 are primary and secondary turns then, Voltage ratio= E1/E2 and Turns ratio of transformer = N1/N2 E1/E2 = N1/N2

Write down the equation for frequency of emf induced in an Altenator.

Description : Write down the equation for frequency of emf induced in an Altenator.

Last Answer : F = (PN)/120 Hz,Where P- Number of poles, N-Speed in rpm

What is the EMF equation of transformer?

Description : What is the EMF equation of transformer?

Last Answer : Erms = 4.44 f Φ maxT volt

How the frequency of rotor emf is related to the slip in an I M?

Description : How the frequency of rotor emf is related to the slip in an I M?

Last Answer : Frequency of rotor emf/current fr=Sf

How the magnitude of rotor emf is related to the slip in an I M?

Description : How the magnitude of rotor emf is related to the slip in an I M?

Last Answer : Rotor circuit emf per phase E2’=SE2

What is the emf equation for DC generator?

Description : What is the emf equation for DC generator?

Last Answer : A = number of parallel paths. That is for lap winding it is equal to Z and for wave winding it equal to 2. 

What is the emf equation for transformer?

Description : What is the emf equation for transformer?

Last Answer : Always maximum flux reaches from zero to maximum in one quarter of the cycle. That is in of second. That is equal to 1/200 second. Average rate of change of flux = Qm / f. = Qm * 4 * f. = 4 f Qm Weber / ... * form factor. ∴ rms. Value of emf = 1.11 * 4 f Qm N volts. = 4.44 f Qm N volts.

What is the emf equation for generator?

Description : What is the emf equation for generator?

Last Answer : emf = P * φ * Z * N / A * 60 Where, φ = Flux per pole in Weber. Z = Total number of armature conductors. P = Number of poles. A = Number of parallel paths in armature. N ... such cases A=2 and in lap wave wound armature parallel paths is equal to the number of poles in the armature winding. 

What is the equation used to find out frequency of number of cycles of induced emf?

Description : What is the equation used to find out frequency of number of cycles of induced emf?

Last Answer : f = NP/120

How we can find the direction of induced emf?

Description : How we can find the direction of induced emf? 

Last Answer : The direction of induced emf can be find out by the Fleming's right hand rule', and lenz's law' Fleming's right hand rule : Fleming's right hand rule states that, if ... that the action of magnetic field set up by induced current tends to opposes the root cause which produces it. 

Why back emf used for a dc motor? highlight its significance.

Description : Why back emf used for a dc motor? highlight its significance.

Last Answer : The induced emf developed when the rotating conductors of the armature between the poles of magnet, in a DC motor, cut the magnetic flux, opposes the current flowing through the conductor, when the ... speed of rotation of the armature conductors. In starting, the value of back emf is zero.

A 4 pole lap wound dc shunt motor rotates at the speed of 1500 rpm, has a flux of 0.4 mWb and the total number of conductors are 1000. What is the value of emf? (A) 100 Volts. (B) 0.1 Volts. (C) 1 Volts. (D) 10 Volts.

Description : A 4 pole lap wound dc shunt motor rotates at the speed of 1500 rpm, has a flux of 0.4 mWb and the total number of conductors are 1000. What is the value of emf? (A) 100 Volts. (B) 0.1 Volts. (C) 1 Volts. (D) 10 Volts.

Last Answer : Ans: D Given N = 1500 rpm, Φ = 0.4 mWb, Z = 1000, P = 4, & A= 4 Therefore, Eb = NΦPZ / 60 A = 1500 x 0.4 x 4 x 1000 x 10^-3 / 60 x 4 = 60/6 = 10 volts

Slip of the induction machine is 0.02 and the stator supply frequency is 50 Hz. What will be the frequency of the rotor induced emf? (A) 10 Hz. (B) 50 Hz. (C) 1 Hz. (D) 2500 Hz.

Description : Slip of the induction machine is 0.02 and the stator supply frequency is 50 Hz. What will be the frequency of the rotor induced emf? (A) 10 Hz. (B) 50 Hz. (C) 1 Hz. (D) 2500 Hz.

Last Answer : Ans: C Given : s = 0.02 ; f = 50 Hz Therefore, frequency of rotor induced emf = s f = 0.02 x 50 = 1.0 Hz

The emf induced in the primary of a transformer (A) is in phase with the flux. (B) lags behind the flux by 90 degree. (C) leads the flux by 90 degree. (D) is in phase opposition to that of flux.

Description : The emf induced in the primary of a transformer (A) is in phase with the flux. (B) lags behind the flux by 90 degree. (C) leads the flux by 90 degree. (D) is in phase opposition to that of flux.

Last Answer : (C) leads the flux by 90 degree.

An electron in potentiometer experiences a force `2.4xx10^(-19)N`. The length of potentiometer wire is 6m. The emf of the battery connected across the

Description : An electron in potentiometer experiences a force `2.4xx10^(-19)N`. The length of potentiometer wire is 6m. The emf of the battery connected across the

Last Answer : An electron in potentiometer experiences a force `2.4xx10^(-19)N`. The length of potentiometer wire is 6m. The emf of ... 6 V B. 9 V C. 12 V D. 15 V

According to Faraday’s law, EMF stands for a) Electromagnetic field b) Electromagnetic force c) Electromagnetic friction d) Electromotive force

Description : According to Faraday’s law, EMF stands for a) Electromagnetic field b) Electromagnetic force c) Electromagnetic friction d) Electromotive force

Last Answer : d) Electromotive force

If the motive for committing a mass shooting against a country music concert was hating country music, would that make the crime worse, or less bad?

Description : If the motive for committing a mass shooting against a country music concert was hating country music, would that make the crime worse, or less bad?

Last Answer : Sounds like a country music song in the making.

Suppose for a minute that Trump is right and that Obama did wiretap Trump. What would Obama's motive have been?

Description : Suppose for a minute that Trump is right and that Obama did wiretap Trump. What would Obama's motive have been?

Last Answer : The motivation would have been the same as if there was a wiretap under a warrant: trying to get evidence of treasonous acts.

Is there an ulterior motive to the flu shot?

Description : Is there an ulterior motive to the flu shot?

Last Answer : Oh my god, seriously? No, there isn’t. There are more readily available so that more people will get them, improving herd immunity.

No one is this nice right, do you think she has a motive?

Description : No one is this nice right, do you think she has a motive?

Last Answer : It sounds fishy. At first blush I thought maybe it was him lurking as her and trying to stay connected. As I think about it more however, I am unsure on that approach. It is ... caused you some concern. Working this through in real life versus social networks would be my best recommendation.

What study have you recently heard of that you feel is a waste of time and money and may even have an ulterior motive behind it?

Description : What study have you recently heard of that you feel is a waste of time and money and may even have an ulterior motive behind it?

Last Answer : Most of them have an ulterior motive. Just find out who paid for it and it will probably become apparent shortly.