Tag: physics

Questions Related to physics

Screw is a/an

physics common machines kinds of simple machines inclined plane, wedge, screw and wheel and axle types of simple machines

  1. lever

  2. gear

  3. inclined plane

  4. wheel

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Correct Option: C
Explanation:

A screw is a modification of an inclined plane . The threads of a screw are like an inclined plane wrapped around a cylinder.

As the inclination of the screw increases, the distance between the threads

physics common machines kinds of simple machines inclined plane, wedge, screw and wheel and axle types of simple machines

  1. increases

  2. decreases

  3. remains the same

  4. may increase or decrease

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Correct Option: B

If the threads of a screw are closer:

physics common machines kinds of simple machines inclined plane, wedge, screw and wheel and axle types of simple machines

  1. mechanical advantage decreases

  2. inclination increases

  3. effort required will be less

  4. all the above

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Correct Option: C
Explanation:

If threads of a screw are closer then inclination decreases so it has became easy to drive screw or effort required will be less.

Which of the following statement is incorrect about the Raman effect?

physics wave optics refraction of water waves reflection and refraction at plane surfaces theories on light

  1. Raman effect can be seen by passing a monochromatic beam of light through benzene

  2. During scattering, the wavelength of the light used may change

  3. The wavelength of the monochromatic light used to show the Raman effect is approximately $4358$ $\overset{o}{A}$

  4. In Raman scattering the wavelength of the scattered light is the same as that of the incident light

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Correct Option: D

Which of the following does not use the application of eddy current?

eddy currents motional emf electromagnetic induction electromagnetic induction and alternating currents physics

  1. Electric power meters

  2. Induction furnace

  3. LED lights

  4. Magnetic breaks in trains

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Correct Option: C
Explanation:

C. LED light.

Because in the given option, Electric power meter, Induction furnace, and magnetic break in trains are the application of eddy current.

Induction Furnace make use of :

eddy currents motional emf electromagnetic induction electromagnetic induction and alternating currents physics

  1. Self induction

  2. Mutual induction

  3. eddy current

  4. none of these

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Correct Option: C
Explanation:

Inductance Furnace makes use of Eddy current. 

Identify the wrong statement

eddy currents motional emf electromagnetic induction electromagnetic induction and alternating currents physics

  1. Eddy currents are produced in a steady magnetic field

  2. Eddy currents can be minimized by using laminated core

  3. Induction furnace uses eddy current to produce heat

  4. Eddy current can be used to produce breaking force in moving trains

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Correct Option: A
Explanation:

Eddy currents comes in picture only when there is change in linked magnetic flux. 

They can be created when a conductor is moving through a magnetic field, or when the magnetic field surrounding a stationary conductor is varying i.e. anything which results in the conductor experiencing a change in the intensity or direction of a magnetic field can produce eddy currents.

Thus  $A$ is the correct option.

Identify the wrong statement.

eddy currents motional emf electromagnetic induction electromagnetic induction and alternating currents physics

  1. Eddy currents are produced in a steady magnetic field.

  2. Eddy currents can be minimized by using laminated core.

  3. Induction furnace uses eddy current to produce heat.

  4. Eddy current can be used to produce breaking force in moving trains.

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Correct Option: A
Explanation:

Eddy currents comes in picture only when there is change in linked magnetic flux. Thus statement A is wrong.

Which of the following law follows when eddy currents are generated?

eddy currents motional emf electromagnetic induction electromagnetic induction and alternating currents physics

  1. Lenz's law

  2. Gauss's law

  3. Both A and B

  4. None of these

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Correct Option: A
Explanation:

Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field.By Lenz's law, an eddy current creates a magnetic field that opposes the change in the magnetic field that created it, and thus eddy currents react back on the source of the magnetic field.Lenz law, the current swirls in such a way as to create a magnetic field opposing the change; for this to occur in a conductor, electrons swirl in a plane perpendicular to the magnetic field.

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Which of the following is true in context of Eddy currents?

eddy currents motional emf electromagnetic induction electromagnetic induction and alternating currents physics

  1. By Lenz's law, an eddy current creates a magnetic field that opposes the magnetic field that created it.

  2. Eddy currents are loops of electrical current induced within conductors by a changing magnetic field in the conductor, due to Faraday's law of induction

  3. Eddy currents are a cause of energy loss in alternating current (AC) inductors, transformers, electric motors and generators etc.

  4. All of the above 

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Correct Option: D
Explanation:

 Eddy currents are loops of electrical current induced within conductors by a changing magnetic field in the conductor, due to Faraday's law of induction,are a cause of energy loss in alternating current (AC) inductors, transformers, electric motors and generators etc.

By Lenz's law, an eddy current creates a magnetic field that opposes the magnetic field that created it.
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