What is transformer in electrical engineering? What type of transformer we use at power stations?

transformer

Transformer

Transformer is a device that can increase or decrease the primary voltage, it is one of the most useful device in electrical engineering specially in power transmission, In street usually step down transformers are used because the source voltage that directly come from grid stations is too high to use consume it to our home electrical appliance so transformers are used to decrease the voltage(usually 220v) so that it can be used at homes without damaging any appliance But at power stations we usually use step up transformers to increase the voltage as in power transmittion current and voltage have inverse relationship  so by increasing the voltage the current will decrease that has a a lot of benefits but one of the biggest benefit is by decreasing current there will be less power loss during power transmitting because according to power formula(P=I^2R) current has square time relationship with power so even small increment in current may cause huge loss so this is why we use step up transformers at power stations.

Bundle of Physics mcq's That you should know before Entrance test

Physics Mcq's

MCQs # 1The periodic alternations of sound between maximum and minimum loudness is called ______.

A.Pitch of sound

B.frequency of sound

C.Beats of sound

D.Quality of sound

Answer:C

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Explanation: It's definition 

MCQs # 21 torr is equal to to:

A.13.3 N/m^2

B.1.33 N/m^2

C.133.3 N/m^2

D.0.133 N/m^2

Answer: C

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MCQs # 3Kilo watt-hour is unit of;

A.Power

B.Work

C.Energy

D.both  B&C

Answer: D

MCQs #4What is average density of earth?

A.5000 kg/m^3

B.5500  kg/m^3

C.4000 kg/m^3

D.4500 kg/m^3

Answer:B

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MCQs #5For a point at the same distance above the surface and below the surface, the acceleration due gravity will decrease more_____.

A.Above the surface

B.Below the surface

C.Same at both points

D. none of them

Answer:A

Explanation: According to relation,

Change in acceleration due to gravity above the surface; g'=g(1-2h/R) 

where h=height g=9.8 m/sec^2 and R=radius of earth

and

Change in acceleration due to gravity below the surface; g'=g(1-d/R) here d=depth;

Now in height relation there is 2 in numerator that means it will be greater value in numerator in height relation than the depth relation when both height and depth are taken same value;Now obviously when we subtract greater value from 1 it will give us lesser value and when lesser value is multiplied with g it will produce smaller value hence a point at the same distance above the surface and below the surface, the acceleration due gravity will decrease more at height than the depth.

MCQs # 6When an elevator goes up with uniform velocity then the apparent weight will be_____.

A.increase by ma

b.decrease by ma

C.remain same as original weight

D.increase by 2ma.

Answer:C

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According to formula ;

                                    Apparent weight=original weight+ma     (here m=mass,a=Acceleration when a body goes up or down)

According to given condition acceleration is zero because of uniform velocity.

hence,

                 Apparent weight=original weight+mx0

                         apparent weight=Original weight 

                              proved..

Q# 7Photon is _______.A.charge-lessB.mass-lessC.Energy-lessD. Both A and  B.Answer: DExplanation: Self defined.

Q# 8The motion under the elastic restoring force is called_________?Answers: Simple harmonic motion.

Explanation: Self defined.

Q# 9_________  is also Helium nuclei.

A.Alpha ParticleB.Beta ParticleC.GammaD.N.O.TAnswer: A

Explanation: Self defined.

Q# 10        The device the converts direct current to alternate current is called_______.A.RectifierB.AmplifierC.GeneratorD. N.O.T
Answer: D.
Explanation: It's Invertor.

Q# 11      Voltage regulator is ______ device.

A.LinearB. Non-LinearC.May be linear or may be non-linearD. N.O.TAnswer:B

MCQs # 12If wavelength of a wave is 12m the first anti-node will be at_______.

A.3m

B.4m

C.6m

D.0m

Answer: A

Explanation:

 First anti-node is equal to wavelength/4 hence 12/4 is equal to 3m..

MCQs # 13If a ball is thrown in projectile motion at 60 degree it goes to a certain range, at what other angle the projectile will arrive at the same range.

A.25 degree

B.30 degree

C.45 degree

D.55 degree

Answer:B

Explanation:  When a body is thrown in projectile motion, there are two possible angles that will reach at same range except when angle is 45 degree body is thrown at certain angle the difference between that angle and 45 degree will be added or subtracted from 45 degree.

 for example: If you have given 60 degree, here we can see that difference between 45 and 60 is of 15 degree Now we will subtract this 15 degree from 45 so we will get 30 degree this is other possible degree that will reach at same range and if we were given 30 degree then we would add 15 degree to 45 so we got 60 degree.

TIP 

           If degree is given above the 45 then difference value will be subtracted and if we have given value less than 45 then we will  add the difference value.

MCQs # 14Who discovered the value of G=6.67 x 10^-11 m3 kg-1 s-2?

A.Newton

B.Maxwell

C.Faraday

D. none of them

Answer D: it is Cavendish.

MCQs # 15Which  fringe is not possible in young's double slit experiment?

A.Zeroth bright fringe

B.1st bright fringe

C.1st dark fringe

D.Zeroth Dark fringe

Answer:D

MCQs # 16

A lens aberration in which multicolored blurredimage is formed is called____?

A.Spherical aberration

B.Chromatic Aberration

C.Concave Aberration

D. none of them

 Answer:B

Explanation: It's definition.

Rest and Motion in Physics

Rest and motion

Rest

Usually we consider rest as any relaxing moment or when you have nothing to do but in physics it has different meaning , In physics rest is defined as any body that does not change it's position with respect other then this body is said to be at rest for example when two bodies are moving with uniform velocities then both bodies will be at rest with respect to each other despite the fact that they are moving but with respect to each other they are not changing their positions.

Motion 

When any body changes it's position with respect to other then this body will said to be in motion, for example a car is passing by you at that moment car is changing it's position with respect to you so car will said to be in motion but point that should be noted here is as the car changes it's position your position is also being changed with respect to car so though you are standing motionlessly but in Physics you will also be considered a body that has motion, similarly as we all know that son do not move but since earth is continuously in motion so the son will also be said in motion.

Physics mcq's with answers and explanation

Physics mcqs

Q#1 Switch is always connected to Phase and in series with load or resistor(true/false).

True

Q#2 The extent of injury caused by electric shock is because of voltage (true/false).

False

It is caused by current

Q#3 DC is more dangerous as compare to AC with respect to extent of injury (true/false).

True

Q#4 Voltmeter should have minimum internal resistance  (true/false).

False

Because the resistor connected with the galvanometer in Voltmeter has high resistance

What is Work done and it's derivative.

work done application and formula

Work done

In our daily life work is considered as doing some effort, but in Physics it has entirely different concept, Any body doing work on other body means the first body is applying some to displace other body in other words if one body changes position of other body by applying some force that means the first body is doing some work over other, it can be expressed in mathematical equation as work done is equal to the product of force and displacement(i,e W=f.d) but when we apply the force at some angle we will have to include cosine function in the equation so it will becomeW=fdcos(theta) here theta is angle at which force is being applied to the body if we further rearrange the equation we will find that work is also product of rate of chsngr of momentum and displacement (i.e)

W=f.d we know that f=ma'

so W=ma.d since a=(vf-vi)/t here vf and vi are the final and initial velocities respectivey

=> W={(mvf-mvi)/t}xd

hence this equation is showing that work can also be defined as product of rate of change of momentum and displacement.

Some important MCQ's

MCQs # 1The periodic alternations of sound between maximum and minimum loudness is called ______.

A.Pitch of sound

B.frequency of sound

C.Beats of sound

D.Quality of sound

Answer:C

Explanation: It's definition 

MCQs # 21 torr is equal to to:

A.13.3 N/m^2

B.1.33 N/m^2

C.133.3 N/m^2

D.0.133 N/m^2

Answer: C

MCQs # 3Kilo watt-hour is unit of;

A.Power

B.Work

C.Energy

D.both  B&C

Answer: D

MCQs #4What is average density of earth?

A.5000 kg/m^3

B.5500  kg/m^3

C.4000 kg/m^3

D.4500 kg/m^3

Answer:B

Multiple choice question(MCQs) of Physics with answers and explanation

Q#1

Photon is _______.

A.charge-less
B.mass-less
C.Energy-less
D. Both A and  B.

Answer: D

Explanation: Self deined.

Q#2

The motion under the elsatic restoring force is called_________?

Answers: Simple hormonic motion.

Explanation: Self deined.

Q#3

_________  is also Helium nuclei.
A.Alpha Particle
B.Beta Particle
C.Gamma
D.N.O.T

Answer: A

Explanation: Self deined.

Q#4
        The device the converts direct current to alternate current is called_______.

A.Rectifier
B.Amplifier
C.Generator
D. N.O.T

Answer: D.

Explanation: It's Invertor.

Q#5
      Voltage regulator is ______ device.

A.Linear
B. Non-Linear
C.May be linear or may be non-linear
D. N.O.T

Answer:B