# E.M.F equation of a transformer

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## Related questions

The e.m.f. 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

These self inductance of a circuit is defined as twice the work done against the induced e.m.f. on establishing unit current in the coil. If the current to be established in the coil is doubled, the work done against the induced e.m.f. will be  1. Doubled  2. Halved  3. four times  4. Quarter times

The back e.m.f of a motor at the moment of starting : -  a) zero b) maximum c) minimum d) optimum

The direction of inducted e.m.f. can be found with the help of (a) Fleming’s right hand rule (b) Kirchhoff’s voltage law (c) Lenz’s law (d) Laplace’s law

Five cells, each with an e.m.f. of 2V and internal resistance of 0.5Ω are connected in series. The resulting battery will have

Which of the following quantity maintains the same direction whether a D.C. machine runs as a generator or as a motor a. Induced e.m.f. b. Armature Current c. Field Current d. Supply Current

In a Synchronous motor, the magnitude of stator back e.m.f (Eb) depends on

The induced e.m.f. in the armature conductors of a d.c. motor is?

The counter e.m.f. of a d.c. motor?

A network which contains one or more than one source of e.m.f. is known as?

The e.m.f. induced in the armature of a shunt generator is 600 V. The armature resistance is 0.1 ohm. If the armature current is 200 A, the terminal voltage will be?

As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit?

Which law states that induced e.m.f and current always opposes the cause producing them?

Define the following terms as referred to battery. a) E.M.F b) Internal resistance c) Ah efficiency d) WAh efficiency

A step-down chopper, fed from a 120 volt DC source, operates a DC motor whose armature e.m.f. and armature resistance are 100 volt and 0.5Ω respectively. With the magnitude control ratio 0.6, the quadrant of operation DC motor is  (a) First (b) Second (c) Third (d) Fourth

A shunt generator running at 1000 r.p.m. has generated e.m.f. as 200 V. If the speed increases to 1200 r.p.m., the generated e.m.f. will be nearly?

The voltage regulation of an alternator having 0.75 leading p.f. load, no-load induced e.m.f. of 2400V and rated terminal voltage of 3000V is —————————————  A) 20% B) —20% C) 150 D) -26.7

"In any network containing more than one sources of e.m.f. the current in any branch is the algebraic sum of a number of individual fictitious currents (the number being equal to the number of sources of e.m.f.), each of which is due to separate action of each source of e.m.f., taken in order ... sources of e.m.f. are replaced by conductors, the resistances of which are equal to the internal resistances of the respective sources". The above statement is associated with?

According to Fleming's right-hand rule for finding the direction of induced e.m.f., when middle finger points in the direction of induced e.m.f., forefinger will point in the direction of?

The equation of 50 Hz current sine wave having r.m.s. value of 60 A is?

The efficiency of a transformer at full load 0.8 p.f lagging is 90%. Its efficiency at full load 0.8 p.f leading will be (1) Less than 90% (2) More than 90% (3) 90% (4) None of these

What is the EMF equation of the transformer?

The characteristic equation of a simple servo system is s2+6s+25=0. Damping factor of the system is: A) 3.2 B) 2.4 C) 1.8 D) 2.9

If the characteristics equation of a closed loop system is s2+2s+2=0, then the system is  (A) Over damped (B) Critically damped (C) Under damped (D) Undamped

Which among the following is the equation for the number of independent loops for a network with n nodes and b branches?  (A) n-1 (B) b+n-1 (C) b-n+1 (D) b-n

In a network containing resistances and reactances the roots of the characteristic equation give for the circuit : (A) The forced response (B) The total response (C) The natural response (D) The damped response

The maximum flux in a transformer is φm when primary voltage is V and the frequency is f. If the primary voltage is 2 V and frequency is f/2, the flux will be (a) 4 φm (b) 0.25 φm (c) φm (d) 0.5 φm

The swing equation for a synchronous machine is based on (A) relative motion between load angle and stator magnetic field (B) maximum power flow possible through a particular point (C) net torque and angular displacement (D) relation between excitation voltage and excitation current