49 total views, 1 views today

**Alternating Voltage and Current MCQs ( Electrical Engineering ) MCQs – ****Electrical Engineering MCQs**

#### Latest Electrical Engineering MCQs

By practicing these MCQs of **Alternating Voltage and Current MCQs ( Electrical Engineering ) MCQs – Latest Competitive MCQs **, an individual for exams performs better than before. This post comprising of objective questions and answers related to **“**Alternating Voltage and Current MCQs ( Electrical Engineering ) Mcqs **“.** As wise people believe “Perfect Practice make a Man Perfect”. It is therefore practice these mcqs of Electrical Engineeringto approach the success. Tab this page to check **“Alternating Voltage and Current MCQs ( Electrical Engineering )”** for the preparation of **competitive mcqs, FPSC mcqs, PPSC mcqs, SPSC mcqs, KPPSC mcqs, AJKPSC mcqs, BPSC mcqs, NTS mcqs, PTS mcqs, OTS mcqs, Atomic Energy mcqs, Pak Army mcqs, Pak Navy mcqs, CTS mcqs, ETEA mcqs** and others.

**Alternating Voltage and Current MCQs ( Electrical Engineering ) MCQs – ****Electrical Engineering MCQs**

The most occurred **mcqs of Alternating Voltage and Current MCQs ( Electrical Engineering )** in past papers. **Past papers of Alternating Voltage and Current MCQs ( Electrical Engineering )** Mcqs. **Past papers of** **Alternating Voltage and Current MCQs ( Electrical Engineering )** Mcqs . Mcqs are the necessary part of any competitive / job related exams. The Mcqs having specific numbers in any written test. It is therefore everyone have to learn / remember the related **Alternating Voltage and Current MCQs ( Electrical Engineering )** Mcqs. The Important series of **Alternating Voltage and Current MCQs ( Electrical Engineering )** Mcqs are given below:

# Generation of an Alternating EMF

**1. Which, among the following, is the correct expression for alternating emf generated?**

a) e=2Blvsin(θ)

b) e=2B^{2}lvsin(θ)**c) e=Blvsin(θ)**

d) e=4Blvsin(θ)**Answer: c****Explanation: The correct expression for alternating emf generated is e=Blvsin(θ). Where B stands for magnetic field density, l is the length of each of the parallel sides v is the velocity with which the conductor is moved and θ is the angle between the velocity and the length.****2. What should theta be in order to get maximum emf?**

a) 0^{0}**b) 90 ^{0}**

c) 180

^{0}

d) 45

^{0}

**Answer: b**

**Explanation: The value of θ should be 90**

^{0}in order to get maximum emf because e = Blvsin(θ) and sin is maximum when θ is 90^{0}.**3. Calculate the maximum emf when the velocity is 10m/s, the length is 3m and the magnetic field density is 5T.**

**a) 150V**

b) 100V

c) 300V

d) 0V

**Answer: a**

**Explanation: We know that: e**

_{max}=Bvl**Substituting the values from the given question, we get e=150V.**

**4. When a coil is rotated in a magnetic field, the emf induced in it?**

a) Is maximum

b) Is minimum

**c) Continuously varies**

d) Remains constant

**Answer: c**

**Explanation: When a coil is rotated in a magnetic field, cross sectional area varies due to which the number of flux lines crossing it varies, which causes the emf to vary continuously.**

**5. emf is zero if the angle between velocity and length is _____**

**a) 0**

^{0}b) 90

^{0}

c) 270

^{0}

d) 45

^{0}

**Answer: a**

**Explanation: If the angle between velocity and length is zero, sinθ=0**

**So, e=Bvlsinθ = 0.**

**6. In an A.C. generator, increase in number of turns in the coil _________**

**a) Increases emf**

b) Decreases emf

c) Makes the emf zero

d) Maintains the emf at a constant value

**Answer: a**

**Explanation: In an A.C. generator, the emf increases as the number of turns in the coil increases because the emf is directly proportional to the number of turns.**

**7. The number of cycles that occur in one second is termed as ___________**

a) Waveform

**b) Frequency**

c) Amplitude

d) Period

**Answer: b**

**Explanation: The number of cycles that occur in one second is known as the frequency. It is the reciprocal of the time period.**

# Waveform Terms and Definitions

**1. The variation of a quantity such as voltage or current shown on a graph is known as ___________****a) Waveform**

b) Peak value

c) Instantaneous value

d) Period**Answer: a****Explanation: The variation of a quantity, which is voltage or current in this case, shown on a graph with the x-axis as time is known as a waveform.****2. What is the duration of one cycle known as _________**

a) Waveform

b) Peak value

c) Instantaneous value**d) Period****Answer: d****Explanation: The duration of one cycle is known as a period. A function which repeats the same waveform at equal intervals of time is known as a periodic function.****3. The repetition of a variable quantity, recurring at equal intervals, is known as ___________**

a) Waveform

b) Instantaneous value**c) Cycle**

d) Period**Answer: c****Explanation: Each repetition of a variable quantity, recurring at equal intervals, is termed as a cycle.****4. The value of a given waveform at any instant time is termed as ___________**

a) Waveform**b) Instantaneous value**

c) Cycle

d) Period**Answer: b****Explanation: Instantaneous value is the value of the waveform at that instant. Hence the value of a given waveform at any instant time is termed as instantaneous value.****5. The maximum instantaneous value measured from zero value is known as?****a) Peak value**

b) Peak to peak value

c) Cycle

d) Period**Answer: a****Explanation: The maximum instantaneous value measured from the zero value is termed as the peak value.**

Inductance In A DC Circuit MCQs

**6. The maximum variation between the maximum positive and the maximum negative value is known as?**

a) Peak value**b) Peak to peak value**

c) Cycle

d) Period**Answer: b****Explanation: The maximum variation between the maximum positive instantaneous value and the maximum negative instantaneous value is the peak-to-peak value.****7. What is the correct relation between the peak value and peak to peak value for a sinusoidal waveform?**

a) Vp=4Vp-p

b) Vp=Vp-p**c) Vp-p=2Vp**

d) Vp=2Vp-p**Answer: c****Explanation: The maximum variation between the maximum positive instantaneous value and the maximum negative instantaneous value is the peak-to-peak value. For a sinusoidal waveform, it is twice the peak value. Hence Vp-p=2Vp.****8. If the peak to peak voltage is 10V, calculate the peak voltage.**

a) 10V

b) 2V

c) 4V**d) 5V****Answer: d****Explanation: Vp-p=2Vp****Substituting the values from the question, we get Vp=5V.****9. If the peak voltage is 9V, calculate the peak to peak voltage.**

a) 9V

b) 20V**c) 18V**

d) 12V**Answer: c****Explanation: Vp-p=2Vp****Substituting the values from the question, we get Vp-p= 18V.**

# Relationship between Frequency, Speed and Number of Pole Pairs

**1. The waveform of the emf generated undergoes one complete cycle when?**

a) Conductors move past north pole

b) Conductors move past south pole**c) Conductors move past north and south poles**

d) Conductors are stationary**Answer: c****Explanation: The waveform of the e.m.f. generated in an a.c. generator undergoes one complete cycle of variation when the conductors move past an N and an S pole.****2. When is the shape of the negative half of the emf waveform equal to the positive half?**

a) When the conductors move past north pole

b) When conductors move past south pole**c) When conductors move past both north and south pole**

d) When conductors are stationary**Answer: c****Explanation: The waveform of the e.m.f. generated in an a.c. generator undergoes one complete cycle of variation when the conductors move past an N and an S pole and the shape of the wave over the negative half is exactly the same as that over the positive half.****3. Which is the correct formula for frequency in an ac generator?****a) f=p*n**

b) f=p/n

c) f=n/p

d) f=n^{2}p**Answer: a****Explanation: The frequency in an ac generator is p*n, where p is pairs of poles and speed is n revolutions per second.****4. What will happen to the frequency if the number of revolutions increases?****a) Increases**

b) Decreases

c) Remains the same

d) Becomes zero**Answer: a****Explanation: We know that:****f=p*n, therefore, as n increases, f also increases.****Hence frequency increases if number of revolutions increases.****5. What happens to the frequency if the number of pairs of poles increases?****a) Increases**

b) Decreases

c) Remains the same

d) Becomes zero**Answer: a****Explanation: We know that:****f=p*n, therefore, as p increases, f also increases.****Hence frequency increases if number of pair of poles increases.****6. Calculate the frequency if the number of revolutions is 300 and the paired poles are 50.****a) 15kHz**

b) 150kHz

c) 1500kHz

d) 150Hz**Answer: a****Explanation: We know that f=p*n****f=50*300=15000 Hz = 15kHz.****7. Calculate the number of revolutions if the frequency is 15kHz and the paired poles are 50.**

a) 100

b) 200**c) 300**

d) 400**Answer: c****Explanation: We know that f=p*n****f=15kHz=15000Hz, p=50****15000=50*n => n=15000/50=300.****8. Calculate the number of paired poles if the frequency id 15kHz and the number of revolutions is 300.**

a) 10

b) 30**c) 50**

d) 70**Answer: c****Explanation: We know that f=p*n****f=15kHz=15000Hz, n=300****15000=p*300 => p=15000/300=50.****9. What is the frequency of a two pole machine having n=50?**

a) 100Hz

b) 200Hz**c) 50Hz**

d) 25Hz**Answer: c****Explanation: For a two pole machine, p=1.****f=pn = 1*50 = 50Hz.****10. What is the minimum number of poles that a machine must have __________**

a) 1**b) 2**

c) 4

d) 10**Answer: b****Explanation: The minimum number of poles that a machine must have is 2 because a machine must have at least one pair of poles = 2 poles.**