MCQs on Electromotive Force

Answer: The correct answer is (c) 4f Φ_m

Explanation: EMF Equation Of The Transformer

Let,

N1 = Number of turns in primary winding

N2 = Number of turns in secondary winding

Φm = Maximum flux in the core (in Wb) = (Bm x A)

f = frequency of the AC supply (in Hz)

The flux rises to its maximum value Φ_m from 0. It reaches the maximum value in one-quarter of the cycle i.e in T/4 sec. Here, T is the time period of the sin wave of the supply = 1/f). Thus, average rate of change of flux = ^Φ_m /_(T/4)    = ^Φ_m /_(1/4f)

Therefore, average rate of change of flux = 4f Φ_m       ....... (Wb/s). 

Induced emf per turn = rate of change of flux per turn.

Therefore, average emf per turn = 4f Φ_m   ..........(Volts).

Answer: The correct answer is (c) Maximum Value

Explanation:  EMF equation of a transformer

E = 4.44fϕmN

Here

• ϕm = Maximum flux
• N = number of turns
• f = frequency
• E = EMF

Answer: The correct answer is (b) Transformer

Explanation: In a transformer, the windings are stationary, the magnetic field induced moves around the conductor and produces the emf. Thus transformer uses the principle of statically induced emf among the available options.

Answer: The correct answer is (a) Self-inductance

Explanation: The property of the coil by which a counter e.m.f. is induced in it when the current through the coil changes is known as self-inductance.

Answer: The correct answer is (c) Generator

Explanation: Dynamic Induced emf is generated when a current carrying conductor cuts the magnetic flux using relative motion. It has rotating parts in it, inducing emf with respect to moving parts is known as dynamic Induced emf. The generator works on the production of dynamically generated e.m.f in the conductors.

Answer: The correct answer is (a) Rate of change of flux

Explanation: Induced emf is directly proportional to the number of turns, magnetic field, area, and the time in which the magnetic flux changes. Thus, the magnitude of the induced emf depends on the change in magnetic flux and also on the time in which the magnetic flux changes.

Answer: The correct answer is (a) 44.2 Watt

Explanation: Power of battery is

P_emf=iE

Power supplied by battery E₁ = I₁E₁=44.2 Watt

Answer: The correct answer is (a) first law

Explanation: When a conductor cuts magnetic flux, an emf is induced in the conductor. Faraday's law of induction is a basic law of electromagnetism predicting how a magnetic field will interact with an electric circuit to produce an electromotive force.

Answer: The correct answer is (a) Fleming

Explanation: Invented in the 19th century by British physicist John Ambrose Fleming for applications in electromagnetism, the right-hand rule is most often used to determine the direction of a third parameter when the other two are known (magnetic field, current, magnetic force).

Answer: The correct answer is (a) Equal to one

Explanation: Transformers that have a ratio of 1 to 1 between the primary and secondary windings are often used to protect secondary circuits and individuals from electrical shocks between energized conductors and earth ground. Suitably designed isolation transformers block interference caused by ground loops.

Answer: The correct answer is (b) 5 Joules

Explanation: The total energy supplied by the battery is 5 Joules. The electromotive force or EMF is the amount of energy supplied by a cell or a battery per coulomb of charge passing through it.

Answer: The correct answer is (c) same terms

Explanation: The terms potential difference and voltage are the same. The potential difference between point A and B is also known as the voltage between point A and point B. 

Answer: The correct answer is (a) Volt

Explanation: It is commonly measured in units of volts, equivalent in the meter–kilogram–second system to one joule per coulomb of electric charge. In the electrostatic units of the centimeter–gram–second system, the unit of electromotive force is the statvolt or one erg per electrostatic unit of charge.