Tag: concept of energy

Questions Related to concept of energy

Lenzs law is a consequence of the law of conservation of:

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. charge

  2. energy

  3. induced emf

  4. induced current

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Correct Option: B
Explanation:

Lenzs law is a consequence of the law of conservation of energy. Emf induced is produced to oppose the motion.

Which one of the following is not the unit of energy?

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. joule

  2. newton metre

  3. kilowatt

  4. kilowatt hour

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Correct Option: C
Explanation:

kilowatt is the unit of power.

joule is the unit of energy (capacity to do work).
newton metre is the unit of work.
kilowatt hour is the commercial unit of energy.
Hence the correct answer is option C.

Electric motor converts electrical energy into

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. Mechanical energy

  2. Sound energy

  3. Thermal energy

  4. Light energy

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Correct Option: A
Explanation:

The electric motor works on principle of electromagnetic induction, which is when a voltage is induced by a changing magnetic field.

A fish swimming in water possess mechanical energy.

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. True

  2. False

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Correct Option: A
Explanation:

The power consumption

 of the undulatory fish swimming is produced by active 
muscles. The mechanical energy generated by stimulated muscles is dissipated partly by the passive tissues of fish.

A particle of mass $m$ is moving in a horizontal circle of radius $r$ with a centripetal force $\vec {F}=\dfrac{-k}{r^{2}}\hat {r}$. The total mechanical energy of the particle is 

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. $\dfrac{-k}{r}$

  2. $\dfrac{3}{2}\dfrac{k}{r}$

  3. $\dfrac{-k}{2r}$

  4. $\dfrac{-3k}{2r}$

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Correct Option: C

Which does not have the same unit as others

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. Watt-sec

  2. Kilowatt-hour

  3. $eV$

  4. $J-sec$

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Correct Option: D

It requires twenty turns of the stem of a watch to wind the main spring and this stores sufficient energy to keep the watch running for 30.0 hour.If ten turns are given to the stem, it will run for:

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. 20 hr

  2. 15 hr

  3. 7.5 hr

  4. 3.75 hr.

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Correct Option: C

Which one of the following units measures energy?

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. Kilo-watt-hour

  2. $(volt)^{2} (\sec)^{-1} (ohm)^{-1}$

  3. $(pascal)(foot)^{2}$

  4. None of the above

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Correct Option: A

How much work will be done in bringing a charge of $10$ milli coulombs from infinity to a point at which potential is $12v$.

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. $1.2J$

  2. $0.12J$

  3. $0 J$

  4. $120 J$

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Correct Option: B
Explanation:

$W=QV$
$=(10\times 10^{-3})(12V)$
$=12\times 10^{-2}J$
$=0.12J$

Erg is a unit of:

physics energy : forms and sources concept of energy energy for everything forms of energy

  1. energy

  2. pressure

  3. force

  4. velocity

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Correct Option: A
Explanation:

The erg is a unit of energy and work equal to 10−7 joules. It originated in the centimetre–gram–second(CGS) system of units. It has the symbol erg. The erg is not an SI unit.