MCQ Questions for Class 11 Engineering Physics Units And Measurement Quiz 4

The dimensions of torque are

0%
$[MLT^{-2}]$
0%
$[ML^2T^{-2}]$
0%
$[ML^2T^{-1}]$
0%
$[M^2L^2T^{-2}]$

How many order of magnitude are there in one million?

0%
5
0%
4
0%
6
0%
None of above

Dimensional formula of power is

0%
$[M^2L^2T^{-2}]$
0%
$[ML^2T^{-3}]$
0%
$[M^2LT^{-2}]$
0%
$[MLT^{-2}]$

Explanation

$Power = force \times velocity$

$P = F \times v$

$F=\left[ ML{ T }^{ -2 } \right]$

$v=\left[ L{ T }^{ -1 } \right]$

Therefpre, the dimensional formula of power,

$P = \left[ ML{ T }^{ -2 } \right] \times \left[ L{ T }^{ -1 } \right] = \left[ M{ L }^{ 2 }{ T }^{ -3 } \right]$

The thickness of a metal sheet is measured to be

$326 mm$ . Express its order of magnitude in mm.

0%
$10^0$
0%
$10^1$
0%
$10^2$
0%
$10^3$

Explanation

Thickness

$t = 326\ mm$

$= 3.26 \times 10^2\ mm$

Hence, order of magnitude in mm is

$10^2$ .

$\mathring{A}$ is equal to :

0%
$0.1$ nm
0%
$10^{-10}$ cm
0%
$10^{-8} m$
0%
$10^{-4} \mu$ .

Explanation

1 Angstorm =

$1 \times 10^{-10}$ m =

$0.1 \ nm$ (

$10^{-9}$ m)

The dimensions of magnetic field in

$M, L, T$ and

$C$ (coulomb) are given as

0%
$[MLT^{-1}C^{-1}]$
0%
$[MT^{2}C^{-2}]$
0%
$[MT^{-1}C^{-1}]$
0%
$[MT^{-2}C^{-1}]$

Explanation

Force

$F$ acting on charge

$q$ moving with velocity

$v$ in magnetic field

$B$ is given as

$F=qvB$ thus

$B=\dfrac {F}{qv}$

$\therefore [B]=\dfrac {[F]}{[qv]}=\dfrac {MLT^{-2}}{C\times LT^{-1}}=[MT^{-1}C^{-1}]$

Which of the following quantities has a unit but dimensionless?

0%
Strain
0%
Reynolds number
0%
Angular displacement
0%
Poisson's ratio

Using mass

$(M)$ , length

$(L)$ , time

$(T)$ and current

$(A)$ as fundamental quantities, the dimension of permeability is

0%
$\displaystyle \left [ M^{-1}LT^{-2}A \right ]$
0%
$\displaystyle \left [ ML^{-2}T^{-2}A^{-1} \right ]$
0%
$\displaystyle \left [ MLT^{-2}A^{-2} \right ]$
0%
$\displaystyle \left [ MLT^{-1}A^{-1} \right ]$

Explanation

Magnetic permeability is a constant of proportionality that exists between magnetic induction and magnetic field intensity.

In SI units, permeability is measured in henries per meter

$H/m$ or

$H m^{-1}$ .

Henry has the dimensions of

$[ML^2T^{-2}A^{-2}]$ .

Dimensions for magnetic permeability will be

$[ML^2T^{-2}A^{-2}]/[L]=$

$[MLT^{-2}A^{-2}]$

The quantity/ quantities that does/do not have mass in its/their dimensions is/are :

0%
specific heat
0%
latent heat
0%
electrical potential difference
0%
electrical resistance

Count total number of Significant Figures in 3.0800

0%
3
0%
5
0%
1
0%
2

Count total number of significant figures in 3500

0%
1
0%
2
0%
3
0%
4

Dimensional formula of power is :
(West Bengal/NTSE Stage-l/2013)

0%
$[M^{2}L^{2}T^{-2}]$
0%
$[ML^{2}T^{-3}]$
0%
$[M^{2}LT^{-3}]$
0%
$[MLT^{-2}]$

Explanation

power

$=\cfrac{work}{time} ; work=force\times displacement ;$

$Force=mass\times acceleration$ ;

$acceleration=\cfrac{velocity}{time}$ ;

$velocity=\cfrac{displacement}{time}$

$acceleration=\cfrac{velocity}{time}=\cfrac{\left[ L \right]}{\left[ T^2 \right] }$

$P=\cfrac{Work}{Time}=\cfrac{Force \times displacement}{Time} =\cfrac{\left[ M \right] \times \cfrac{\left[ L \right]}{\left[ T^2 \right] } \times L}{T}=\cfrac{\left[ MLL \right] }{T^3}=\left[ ML^2T^{-3} \right]$

Hence, option

$B$ is correct.

A physical quantity

$X$ is expressed as velocity

$\displaystyle =\sqrt{\dfrac{X}{Density}}$ The dimension of

$X$ are

0%
$ML^{-1}T^{-2}$
0%
$MLT^{-2}$
0%
$MLT^{-1}$
0%
$ML^{-1}T^{-3}$

Explanation

$[X]=[(velocity)^{2}Density]$

$=[(L^{2}T^{-2})ML^{-3}]=[ML^{-1}T^{-2}]$

Count total number of significant figures in 0.00418

0%
5
0%
4
0%
3
0%
6

The magnetic moment has dimensions of

0%
$\left [LA\right ]$
0%
$\left [L^{2}A\right ]$
0%
$\left [LT^{-1} A\right ]$
0%
$\left [L^{2} T^{-1} A\right ]$

Explanation

Magnetic moment of a coil carrying current is,

$M = I.A$

[A is area of cross section and i is current]

Dimension of $M = AL^{2}$

Which of the following physical quantities do not have same dimensions?

0%
Pressure and stress
0%
Tension and surface tension
0%
Strain and angle
0%
Energy and work

Which of the following pair of quantities do not have the same dimensions?

0%
Potential gradient, electric field
0%
Torque, kinetic energy
0%
Light year, time period
0%
Impedance, reactance

The thickness of a newspaper sheet is of the order of

0%
0.1 m
0%
0.1 cm
0%
0.1 mm
0%
1 micrometre

If the units of mass, length and time are doubled, then what happen to the unit of 'relative density'?

0%
doubled
0%
remains same
0%
tripled
0%
equatrepled

State whether the following statement is True or False.

The prefix used for

$\displaystyle { 10 }^{ 3 }$ is kilo.

0%
True
0%
False

Explanation

The prefix used for

$\displaystyle { 10 }^{ 3 }$ is kilo and it means 1000.

The prefix used for denoting an order of magnitude of

$\displaystyle { 10 }^{ 6 }$ is ___________.

0%
Giga
0%
Kilo
0%
Mega
0%
Micro

Explanation

Mega is the prefix used for denoting an order of magnitude of

$10^6$ .

For example :

$10^6\ Watt$ is also termed as

$Megawatt$

The dimensions of Planck's constant are

0%
$\left [ML^{-3} T^{-1}\right ]$
0%
$\left [ML^{-2} T^{-1}\right ]$
0%
$\left [M^{0}L^{-1} T^{-3}\right ]$
0%
$\left [ML^{2} T^{-1}\right ]$

Explanation

$E = hv$ , h is Planck's constant

$\left [h\right ] = \dfrac {\left [E\right ]}{\left [v\right ]} = \dfrac {ML^{2}T^{-2}}{T^{-1}} = ML^{2} T^{-1}$

The error in measurement caused by positioning the eye incorrectly is called

0%
parallel error
0%
standard error
0%
eye error
0%
parallax error

Why are metre scales are made very thin?

0%
To avoid breakage and parallax
0%
To avoid parallax and error in measurement
0%
To avoid breakage and error in measurement
0%
To make it cheap

Which of the following is not a reading of meter scale?

0%
$2.5 cm$
0%
$15 cm$
0%
$1.5 mm$
0%
$0.4 m$

Explanation

Meter scale has least count

$0.1cm=1mm$ so reading should be

$integral$

$multiple$ of

$1mm$ .

$2.5cm=25mm$ possible

$15cm=150mm$ possible

$0.4m=400mm$ possible

$1.5mm=1.5\times 1mm$ not possible because

$1.5$ is not an

$integer.$

The relation between force 'F' and density 'd' is

$F=\displaystyle\frac{x}{\sqrt d}$ . The dimensions of

$x$ are

0%
$\displaystyle [L^{-1{/2}}M^{3{/2}}T^{-2}]$
0%
$\displaystyle [L^{-1{/2}}M^{1{/2}}T^{-2}]$
0%
$\displaystyle [L^{-1}M^{3{/2}}T^{-2}]$
0%
$\displaystyle [L^{-1}M^{1{/2}}T^{-2}]$

Explanation

The dimensions of

$x$ are

$[x]=[F]{ [d] }^{ 0.5 }=[ML{ T }^{ -2 }]{ [{ ML }^{ -3 }] }^{ 0.5 }=[{ M }^{ 1.5 }{ L }^{ -0.5 }{ T }^{ -2 }]$

Which method is used by astronomers to calculate how far the star is?

0%
Parallax
0%
Equillax
0%
Purplex
0%
None

The dimensional formula for Reynold's number is ________.

0%
$[L^0M^0T^0]$
0%
$[L^1M^1T^1]$
0%
$[L^{-1}M^1T^1]$
0%
$[L^1M^1T^{-1}]$

Explanation

The formula for Reynold's number is:

$Re=\dfrac { \rho vd }{ \mu } \\ \Rightarrow [Re]=\dfrac { [\rho ][v][d] }{ [\mu ] } =\dfrac { [M{ L }^{ -3 }][L{ T }^{ -1 }][L] }{ [{ ML }^{ -1 }{ T }^{ -1 }] } =[{ M }^{ 0 }{ L }^{ 0 }{ T }^{ 0 }]$ .

Thus, Reynold's number is a dimensionless quantity. It is defined as the ratio of inertial force to viscous force, so it has to be a dimensionless number.

The dimensions of Planck's constant is the same as the product of

0%
force and time
0%
force, displacement and time
0%
force and distance
0%
time and displacement

Explanation

$E=h\nu$

$\implies$ Planck's constant

$h=\dfrac{E}{\nu}$
Dimension of energy=

$[ML^2T^{-2}]$

Dimension of

$\nu=[T^{-1}]$

Thus dimension of

$h=[ML^2T^{-1}]$

Dimension of Force

$=[MLT^{-2}]$

Dimension of Displacement=

$[L]$

Dimension of Time

$=[T]$

Thus dimension of

$Force\times displacement\times time=[ML^2T^{-1}]$ =Dimension of Planck's constant

The physical quantity having the dimensions

$\displaystyle \left[ { M }^{ -1 }{ L }^{ -3 }{ T }^{ 3 }{ A }^{ 2 } \right]$ is :

0%
Resistance
0%
Resistivity
0%
Electrical conductivity
0%
Electromotive force

Explanation

Electrical conductivity is given by :

$\rho =R\dfrac { A }{ l }$ =

$\dfrac { {n e }^{ 2 }\tau }{ m }$

Dimensions of

$A$ =

${ L }^{ 2 }$

Dimensions of

$l$ =

${ L }^{ 1 }$

Dimensions of

$R$ =

${ M }^{ -1 }{ L }^{ -4 }{ T }^{ 3 }{ A }^{ 2 }$

$=$ number of electrons per unit volume

$={ L }^{ -3 }$

Dimensions of

$e=C^2={AT}^2$

where,

$C=$ coulomb;

$A=$ Ampere;

$T=$ time

Dimensions of

$\tau$

$=T$

Dimension of mass

$m =M$

Dimensions of

$\rho =\dfrac { { A }^{ 2 }{ T }^{ 2 }{ T }^{ 1 } }{ M } \times \dfrac { 1 }{ { L }^{ 3 } }$

$={ M }^{ -1 }{ L }^{ -3 }{ T }^{ 3 }{ A }^{ 2 }$

Hence, option C is correct.

Which of the following is the parallax angle in the shown diagram?

0%
d
0%
p
0%
q
0%
r

Explanation

The parallax angle is the angle between the Earth at one time of year, and the Earth six months later, as measured from a nearby star. Astronomers use this angle to find the distance between the Earth and the Star.

Thus

$p$ is the parallax angle.

Parallax method is suitable for the measurement of:

0%
ball
0%
planet
0%
vehicle
0%
distance between cities

What is the approximation made in the parallax method?

0%
All distances measured between two points on earth is zero.
0%
All distances measured between two points on earth is constant.
0%
Distance between a point on the earth and the planet is very large as compared to the distance between two points on earth's surface.
0%
No approximation is made.

The relation between

$\theta$ ,

$b$ and

$D$ is:
(where

$\theta$ is the parallax angle,

$b$ is the distance between two points of separation,

$D$ is the distance of source from any point of observation)

0%
$\theta = \dfrac{b}{D}$
0%
$\theta=\dfrac{D}{b}$
0%
$\theta = b\times D$
0%
$\theta = b^2\times D$

Explanation

From the figure,

$\tan\theta=\dfrac{b}{D}$

For small angle, we have

$\tan\theta \sim \theta$

So, we get

$\theta=\dfrac{b}{D}$

Which of the following represent the number 300,000,000 :

0%
$3 \times 10^6$
0%
$3 \times 10^7$
0%
$3 \times 10^8$
0%
$3 \times 10^9$
0%
$3 \times 10^{-9}$

Explanation

The given number:

$300,000,000 =3 \times 10^8$

Students A,B and C measure the diameter of a copper ball using the same screw gauge. A takes 5 readings, B takes 9 readings and C takes 8 readings. The measured value will be most accurate for

0%
B
0%
A
0%
C
0%
all

$1$ femtometre is equivalent to

0%
$10^{15} m$
0%
$10^{-12} m$
0%
$10^{-15} m$
0%
$10^{-9} m$

Explanation

$1$ femtometre

$=10^{-15} m$

Which of the following is the best method to measure microscopic distances?

0%
Optical microscope
0%
Meter scale
0%
Screw gauge
0%
Diffraction pattern

Which of the following is the smallest unit?

0%
millimetre
0%
angstrom
0%
fermi
0%
metre

Explanation

Hint:- Convert all units in meter(SI unit) to check the smallest unit.

Explanation:-

$\bullet$ Metre is the SI unit of length.

$\bullet$

$1 \ millimetre = 10^{-3} \ metre$

$\bullet$

$1 \ angstrom = 10^{-10} \ metre$

$\bullet$

$1 \ fermi = 10^{-15} \ metre$
So, fermi is the smallest unit.

$\textbf{Hence option C correct}$

To minimise parallax error, the observer should place the object :

0%
as near to the scale of the ruler as possible and the eye must be directly above the scale
0%
as far to the scale of the ruler as possible and the eye must be directly above the scale
0%
as near to the scale of the ruler as possible and the eye must be to the right of the scale
0%
as near to the scale of the ruler as possible and the eye must be to the left of the scale

Explanation

$Answer:-$ A

There are three simple ways of reducing parallax error in that case:
1. Attach a straight object (like a ruler or straightened paperclip) to the thing you're measuring the displacement of, it should stick out of the object perpendicularly to the scale you're measuring the displacement on.
2. Make sure that object is as close to your scale as possible, but not touching.
3. Put your eyes level with the object, and as close to it as you safely can.

Parallax method is useful

0%
for measuring speed of the light.
0%
for measuring distances of star.
0%
for finding the intensity of the light.
0%
None of the above.

Explanation

$Answer:-$ B

Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. Astronomers use the principle of parallax to measure distances to the closer stars.

$n$ denotes a positive integer,

$h$ the Plancks constant,

$q$ the charge and

$B$ the magnetic field, then the quantity

$\begin{pmatrix} \dfrac{nh}{2\pi qB}\end{pmatrix}$ has the dimension of

0%
Area
0%
Length
0%
Speed
0%
Acceleration

Explanation

Since

$qvB=F$

$\implies qB=\dfrac{F}{v}$

which has dimensions

$[MT^{-1}]$

$h$ has dimensions

$[ML^2T^{-1}]$

Hence the dimension of

$(\dfrac{nh}{2\pi qB})$ is

$[L^2]$ , which is that of area.

Parallax is the apparent displacement of an object because of:

0%
change in observer's point of view
0%
change in object's position
0%
changes both in observers point of view and object's position
0%
consistency in observer's point of view

The effect of parallax is used to measure:

0%
distances to nearby objects
0%
distances to nearby stars
0%
nearness of atoms in substances
0%
the object and image distance in optical experiments

Which of the following statements regarding dimensions is correct?

0%
The dimension of any physical quantity includes the power fundamental physical quantities.
0%
Radian is a fundamental physical quantity having dimension.
0%
Mutual inductance has no dimension.
0%
Dimension of work is same as rate of work done

Explanation

Dimensional formula includes power of fundamental quantites.

For example ; Unit of force is [

$M^1L^1T^{-2}$ ]

Radian is not a fundamental physical quantity it comes under supplementary units.

Dimension of work is

$[M^1 L^2 T^{-2}]$ whereas rate of doing work is

$[M^1 L^2 T^{-3}]$

In which of the following pairs, the two physical quantities have different dimensions?

0%
Plancks constant and angular momentum
0%
Impulse and linear momentum
0%
Moment of inertia and moment of a force
0%
Energy and torque

Explanation

Both plank's constant and angular momentum have dimensions

$[ML^2T^{-1}]$

Both impulse and linear momentum have dimensions

$[MLT^{-1}]$

Moment of inertia has dimensions

$[ML^2]$

Moment of force has dimensions

$[ML^2T^{-2}]$

Both energy and torque have dimensions

$[ML^2T^{-2}]$

Parallax method is based on which of the following principle?

0%
Disparity
0%
Lutz Kelker bias
0%
Trilateration
0%
Triangulation

Error due to eye vision is termed as :

0%
climax error
0%
sight error
0%
parallax error
0%
visional error

Explanation

$Answer:-$ C

Parallax also affects optical instruments such as rifle scopes, binoculars,microscope and twin lens reflex cameras that view objects from slightly different angles. Many animals, including humans, have two eyes with overlapping visual fields that use parallax to gain depth perception; this process is known as stereopsis.

A star's distance (

$d$ ) and its parallax angle (

$p$ ) are related to each other as:

0%
$d=\dfrac{1}{p}$
0%
$d=\dfrac{1}{p^2}$
0%
$p=\dfrac{1}{d^2}$
0%
none of these

Explanation

Astronomers use an effect called parallax to measure distances to nearby stars. Parallax is the apparent displacement of an object because of a change in the observer's point of view.

The relationship between a star's distance and its parallax angle:

$d=\dfrac{1}{p}$

The distance $d$ is measured in parsecs and the parallax angle $p$ is measured in arc seconds.

A physical quantity has term of velocity,and force which are proportional to it .It is known that it does not depend on any other physical quantity ,so its dimension can be,

0%
$ML^{2}T^{-3}$
0%
$MLT^{3}$
0%
$ML^{2}T^{3}$
0%
none of the above

Explanation

Let,

$x$ be the physical quantity.

Here,

$x\propto v$ a

$x\propto F$ where

$v=$ velocity and

$F=$ force

$x=kvF$ where

$k=$ proportionality constant.

Dimensionally,

$[x]=[LT^{-1}][MLT^{-2}]=[ML^2T^{-3}]$

CBSE Questions for Class 11 Engineering Physics Units And Measurement Quiz 4 - MCQExams.com

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Practice Class 11 Engineering Physics Quiz Questions and Answers

CBSE Questions for Class 11 Engineering Physics Units And Measurement Quiz 4 - MCQExams.com

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Practice Class 11 Engineering Physics Quiz Questions and Answers

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