Tag: measurements and units

Questions Related to measurements and units

Name the physical quantity related to the following unit : watt.

physics measurements and units kinds of units fundamental quantities standardized measurement

  1. $Force$

  2. $Power$

  3. $Work$

  4. $Pressure$

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Correct Option: B
Explanation:

Watt is  the SI unit of power, equivalent to one joule per second.

Power $=$ force $\times$ velocity $=$ Work/time
So, $watt=Nms^{-1}=J/s$

Name the physical quantity related to the following unit : pascal.

physics measurements and units kinds of units fundamental quantities standardized measurement

  1. $Force$

  2. $Pressure$

  3. $Work$

  4. $Distance$

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Correct Option: B
Explanation:

The pascal (symbol: Pa) is the SI derived unit of pressure, internal pressure, stress, Young's modulus.

Pressure $=\dfrac{Force}{Area}$ 
So, $1\ pascal=1\ N/m^2$

Column I gives three physical quantities. Select the appropriate units for these from the choices given in column II. Some of the physical quantities may have more than one choice.

Column-I Column - II
a) Capacitance d) Ohm second
b) Inductance e) Coulomb$^{2}$ joule$^{ -1 }$
c) Magnetic induction f) Coulomb volt$^{ -1 }$
g) Newton (ampere/metre)$^{ -1 }$
h) Volt second (ampere)$^{ -1 }$
physics measurements and units kinds of units fundamental quantities standardized measurement

  1. a-e,f; b-d,h; c-g

  2. a-h; b-d; c-e

  3. a-e; b-g,h; c-g

  4. a-e,f; b-d,h; c-d,e

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Correct Option: A
Explanation:

Capacitance is charge per unit volt. 

Volt has unit of work per unit chage. 
So capacitance has units of charge square per unit energy. 
Inductance is defined as volt per unit rate of change of current and voltage per unit current is resistance, so inductance is ohm second. 

The SI unit of magnetic permeability is

physics measurements and units kinds of units fundamental quantities standardized measurement

  1. ${ Am }^{ -1 }$

  2. ${ Am }^{ -2 }$

  3. ${ Hm }^{ -2 }$

  4. ${ Hm }^{ -1 }$

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Correct Option: D
Explanation:

The correct option is D.

The magnetic permeability of any material is its property for allowing the magnetic line of force to pass through it. Therefore, the magnetic material can support the development of the magnetic field. This capability is measured by the magnetic permeability. Also, the magnetic line of force is directly proportional to the conductivity of the material. Its SI unit is Henry per meter i.e. $Hm^{-1}$ or newton per ampere square.

$\left( Coulomb \right) ^{ 2 }{ J }^{ -1 }$ can be the unit of :

physics measurements and units kinds of units fundamental quantities standardized measurement

  1. electric resistence

  2. electric energy

  3. electric capacity

  4. electric power

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Correct Option: C
Explanation:

Electric energy $=ML^{2}T^{-2}$
Electric power $=ML^{2}T^{-3}$
Electric resistance $= ML^{2}I^{-2}T^{-3}$
Electric capacity $=M^{-1}L^{-2}I^{2}T^{4}$$=\left ( \dfrac{I^{2}T^{2}}{(M^{1}L^{2}T^{-2})} \right )=\left ( \dfrac{Q^{2}}{J} \right )$
Hence, option C is correct.

joule is the unit of

physics measurements and units kinds of units fundamental quantities standardized measurement

  1. heat

  2. temperature

  3. thermometry

  4. work

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Correct Option: A,D
Explanation:

Joule is unit of heat , energy and work.

The unit of electric field intensity is:

physics measurements and units kinds of units fundamental quantities standardized measurement

  1. Newton/ metre

  2. Coulomb/ newton

  3. Newton/ coulomb

  4. Joule/ newton

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Correct Option: C
Explanation:

Electric field due to a charge is given by  $E = \dfrac{F}{q}$
Unit of force is Newton $(N)$ and that of charge is Coulomb $(C)$.
So, unit of electric field is  Newton/coulomb  i.e  $N/C$

The energy which an electron acquires when accelerated, through a potential difference of $1$ volt is called

physics measurements and units kinds of units fundamental quantities standardized measurement

  1. $1$ Joule

  2. $1$ eV

  3. $1$ erg

  4. $1$ watt

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Correct Option: B
Explanation:

The energy which an electron acquires when accelerated, through a potential difference of 11 volt is called 1 eV. It is a unit of energy.  It is usually used as a measure of particle energies although it is not an SI (System International) unit. The SI unit for energy is the Joule. $1\,eV=1.602\times 10^{-19}\,Joules$

The Sl unit of length is the meter. Suppose we adopt a new unit of length which equals to $x$ meters. The area 1 $m ^ { 2 }$ expressed in terms of the new unit has a magnitude:

physics measurements and units kinds of units fundamental quantities standardized measurement

  1. $x$

  2. $x ^ { 2 }$

  3. $\dfrac { 1 } { x }$

  4. $\dfrac { 1 } { x ^ { 2 } }$

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Correct Option: D
Explanation:

SI unit of Length $=$ meters.

New Unit of Length $=x$ meters.

$1m=\dfrac 1x$ new units

SI unit of area : 

$A= 1m^2$   

$=1\times 1m^2$                        

$=\dfrac 1x\times \dfrac 1x $     

$=\dfrac{1}{x^2}$     

If $10 ^ { 7 }$ era is taken as unit of energy, $10 ^ { 5 }$ dyne as the unit of force, one second as unit of time. what is, the unit of length?

physics measurements and units kinds of units fundamental quantities standardized measurement

  1. $1$ $m$

  2. $10$ $m$

  3. $100$ $m$

  4. None

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Correct Option: A