Question.
Answer
Question. From NCERT
The dimensional formula of the coefficient of thermal conductivity is :
1.
2.
3.
4.
Answer
The for the coefficient of thermal conductivity isTRICKThermal Conductivity-Speed of Heat Flow per unit Area and TemperatureDimensional formula of
The correct option is D.
Question. From Derived NCERT
If L,Q,R represent inductance, charge and resistance respectively, the units of
[This question includes concepts from 12th syllabus]
1. will be those of current
2. will be those of energy
3. will be those of current
4. will be those of power
Question.
Question.From NCERT
The dimension of ( is the permittivity of free space and is electric field), is
Answer
We know that the given equation gives the energy
density for a capacitor. Dimensions of energy density
can be found as Electrical Energy divided by
Volume, or
Question.
The quantity has dimensional formula same as [This question includes concepts from 12th syllabus]
1.
2.
3.
Answer
3
Question.From NCERT PMT - 1989
Light year is a unit of
(1) Time
(2) Mass
(3) Distance
(4) Energy
Answer
3
Question.From NCERT
The magnitude of any physical quantity:
(1) depends on the method of measurement.
(2) does not depend on the method of measurement.
(3) is more in the SI system than in the CGS system.
(4) is directly proportional to the fundamental units of mass, length and time.
Answer
Question.From NCERT PMT - 1990
Which of the following is not equal to watt ?
(1) Joule/second
(2) Ampere volt
(3) (Ampere)2 ohm
(4) Ampere/volt
Question.From NCERT PMT - 1984
is the unit of
Answer
We know that:.
So the unit of momentum will be equal to .
Question. From NCERT
Which one of the following quantities has not been expressed in proper units ?
Answer
Stress has the units of Force/Area = ,
while strain (=) is dimensionless. So option A is correct.
Surface tension is Force/Length, thus , hence B is also correct.
Energy has the units of , hence the units have to be . Thus C is incorrect option.
Pressure is Force/Area = , thus D is again correct.
Surface tension is Force/Length, thus , hence B is also correct.
Energy has the units of ,
Pressure is Force/Area = , thus D is again correct.
Question.From NCERT
One second is equal to :
(1) 1650763.73 time periods of clock
(2) 652189.63 time periods of clock
(3) 1650763.73 time periods of clock
(4) 9192631770 time periods of clock
Answer
4
Question. From NCERT PMT - 1985
The unit of power is :
(1) Joule
(2) Joule per second only
(3) Joule per second and watt both
(4) Only watt
Answer
Question.From NCERT PMT - 1984
SI unit of pressure is
(1) Pascal
(2)
(3) cm of Hg
(4) Atmosphere
Answer
1
Question.From NCERT PMT - 1992
The unit of Stefan's constant is : [This question includes concepts from Thermal Properties of Matter chapter]
(1)
(2)
(3)
(4)
Answer
Stefan's law is
where,
Question.From NCERT PMT - 1993
In , S is measured in metres and t in seconds. The unit of c is
(1) None
(2) m
(3)
(4)
Answer
4
Question.From NCERT PMT - 1990
Joule-second is the unit of :
(1) Work
(2) Momentum
(3) Pressure
(4) Angular momentum
Answer
Joule is a unit of energy and second
is the unit of time. Thus, has dimensions
Now, energy cannot be the answer since energy has Joule as its unit and cannot be Joule-seconds.
Momentum can't be the answer as momentum is force X time which has dimensions
Angular momentum is given by cross product of linear momentum and radius vector thus it has dimensions , which is the correct answer.
Finally, Power is force times velocity, so its dimensions are
Now, energy cannot be the answer
Momentum can't be the answer as
Angular momentum is given by cross
Finally, Power is force times velocity,
Question.
Electron volt is a unit of
(1) Charge
(2) Potential difference
(3) Momentum
(4) Energy
Answer
The electron volt (symbol eV; also written electronvolt)
is a unit of energy equal to approximately
1.60210 joule (SI unit J).
By definition, it is the amount of energy gained by the charge of a single electron moved across an electric potential difference of one volt.
Hence, the correct option is
Question.From NCERT
Temperature can be expressed as a derived quantity in terms of any of the following
1. Length and mass
2. Mass and time
3. Length, mass, and time
4. None of these
Answer
Temperature is a fundamental quantity,
so it can not be expressed as a
derived quantity in terms of length, mass and time.The correct option is D.
Question.From NCERT
Answer
Answer is B
Question.From NCERT
Which is the correct unit for measuring nuclear radii
(1) Micron
(2) Millimetre
(3) Angstrom
(4) Fermi
Answer
4
Question.From NCERT
Volt/metre is the unit of
(1) Potential
(2) Work
(3) Force
(4) Electric field intensity
Answer
The electric field intensity is given as:
Its unit is
Question.From NCERT PMT - 1983
The unit of self inductance of a coil is
(1) Farad
(2) Henry
(3) Weber
(4) Tesla
Answer
The self-inductance of a coil is given as:
Question.From NCERT PMT - 2005
If the unit of length and force be increased four times, then the unit of energy is
1. Increased 4 times
2. Increased 8 times
3. Increased 16 times
4. Decreased 16 times
Answer
3
Question.From NCERT
Ampere - hour is a unit of
(1) Quantity of electricity
(2) Strength of electric current
(3) Power
(4) Energy
Answer
Ampere-hour is the unit of quantity of electricity or quantity of electric charge.Power is measured in Watt.Energy is measured in Joules.Strength of current ia measured in Amperes.
Hint: Use principle of Homogeneity and remember that rate of flow of charge through a point is known as current.
Formula used:
Here Q is the charge flowing through a point at a time period t.
Complete step by step solution:
We know Ampere is a unit of current and its dimension is
So dimension of Ampere hour is
Also, since current ;
we can see that charge and Ampere hour has a same dimension of
Using the principle of homogeneity we can say that Ampere hour represents the amount of charge.
Just like how mass is a measure of the amount of matter in a system, charge can be seen as a measure of the amount of electrified matter or the Quantity of electricity present in the system.
So we can conclude that ampere hour is a measure of quantity of electricity (which is equivalent to the amount of electric charge)
Thus, the correct option is C.
Additional Information:
The SI unit of charge is coulomb.
1 ampere hour is the amount of charge transferred if 1A current passes through a region for 1hour.
Since coulomb represent the flow in seconds
1 Ampere hour
(Ah is a symbol used for ampere hour.)
Note: The principle of homogeneity is not true for all cases .Since the ratios, constants, or trigonometric quantities have no dimension, their presence or absence in an equation cannot be determined.
Also, sometimes comparing dimensions would not give a correct significance of a quantity. For example: Though Torque and Energy have the same dimension, we cannot say - Joules represent the Moment of force on a body.
Question.From NCERT
The unit of specific resistance is
(1) Ohm / cm2
(2) Ohm / cm
(3) Ohm - cm
(4) (Ohm - cm)-1
Answer
4
Question.From NCERT
The binding energy of a nucleon in a nucleus is of the order of a few
(1) eV
(2) Ergs
(3) MeV
(4) Volts
Answer
Atomic energies are of order of electron volts and kilo electron volts but binding energy of nucleus that is energy required to keep the nucleus together has very high magnitude. It is of the order of Mega electron volt.
Question.From NCERT
If u1 and u2 are the units selected in two systems of measurement and n1 and n2 their numerical values, then
(1)
(2)
(3)
(4)
Answer
1
Question. From NCERT
Universal time is based on :
(1) Rotation of the earth on its axis
(2) Earth's orbital motion around the Sun
(3) Vibrations of cesium atom
(4) Oscillations of quartz crystal
Answer
Universal Time (UT) is a time standard based on Earth's rotation.
Based on the rotation of the Earth, time can be measured by
observing celestial bodies crossing the meridian every day.
Astronomers found that it was more accurate to establish time
by observing stars as they crossed a meridian rather than by
observing the position of the Sun in the sky. The rotation of the
Earth and UT are monitored by the International Earth Rotation
and Reference Systems Service (IERS).
Question. From NCERT PMT - 1984
Unit of stress is
(1)
(2)
(3)
(4)
Answer
4
Question.From NCERT
Unit of magnetic moment is
(1)
(2)
(3)
(4)
Question.From NCERT
One pico Farad is equal to
(1)
(2)
(3)
(4)
Answer
3
Question.From NCERT PMT - 1993
In SI, Henry is the unit of
(1) Self inductance
(2) Mutual inductance
(3) (1) and (2) both
(4) None of the above
Answer
3
Question.From NCERT PMT - 1986
The unit of is
(1) Joule
(2) Joule-Coulomb
(3) Volt–Coulomb
(4) Joule/Coulomb
Answer
4
Question.
The unit of e.m.f. of a cell is:
Answer
Electromotive force or e.m.f is defined as the battery's
energy per Coulomb of charge passing through it.
like other measures of energy per charge emf has
SI unit of volts , equivalent to joules per coulomb.
Question.From NCERT
Unit of self inductance is [This question includes concepts from 12th syllabus]
(1)
(2)
(3)
(4)
Answer
2
Self-inductance of a coil is defined as the phenomenon due to which an emf is induced in a coil when the magnetic flux of coil , linked with the coil changes or current in coil changes . Its S.I. unit is
Question.From NCERT
To determine Young's modulus of a wire, the formula is where L = length, A = area of cross-section of the wire, change in length of the wire when stretched with a force F. The conversion factor to change it from CGS to MKS system is
(1) 1
(2) 10
(3) 0.1
(4) 0.01
Answer
Hint: Young’s modulus is dependent on factors such as force, length and are inversely dependent on factors such as area. Now, we know the SI units of the same which are in the MKS system. To find the factor, equate the units in CGS system and MKS system and find the factor by which it varies.
Complete Step by Step Solution:
Young’s modulus, also called as modulus of elasticity, is the measure of the tensile stiffness of the given material. It also measures the stiffness of the material when there is a force applied on it which causes the change in length due to compression or expansion. Young’s modulus directly depends upon the force applied on the body and inversely varies upon the area of the surface where the force is applied. This can be represented mathematically as,
Where, F is the force applied and A is the area of the surface.
Force in the CGS unit is measured in dyne and area is measured in centimeters. In the MKS system, the force is measured as Newton’s and area and change in length are measured in meters. Using this the units for young’s modulus is given as,
in CGS unit and
in MKS units
Now, taking the CGS equation, we know that
. Substituting this in the equation we get,
We know that
. Substituting this , we get
On further simplification, we get,
Taking the common term to the numerator ,we get
Hence,
Therefore, option (c) is the right answer for the given question.
Note: The CGS system is abbreviated as Centimeter-Gram-Second system, which is a type of Standard Unit system that is quite useful in measuring small quantities in chemical fields. MKS system abbreviated as Meter-Kilogram-Second is used for standard measurements globally across various fields.
Question.From NCERT PMT - 1994
Young's modulus of a material has the same units as
(1) Pressure
(2) Strain
(3) Compressibility
(4) Force
Answer
1
Question.From NCERT PMT - 1997
The units of modulus of rigidity are
(1)
(2)
(3)
(4)
Answer
4
Question.From NCERT
The unit of absolute permittivity is
(1) (Farad-metre)
(2) (Farad/metre)
(3) (Farad/)
(4) F (Farad)
Answer
2
Question. From NCERT
List-I I. Joule II. Watt III. Volt IV. Coulomb
| List-II A. Henry × Amp/sec B. Farad × Volt C. Coulomb × Volt D. Oersted × cm E. Amp × Gauss F. Amp2 × Ohm |
[This question includes concepts from 12th syllabus]
Codes:
(1)
(2)
(3)
(4)
Answer
2
Question.From NCERT PMT - 1997
Which relation is wrong?
(1) 1 Calorie = 4.18 Joules
(2)
(3)
(4)
Answer
4
Question.From NCERT
Match the following:
List-I | List-II | ||
(a) | Distance between earth and stars | 1. | Microns |
(b) | Inter-atomic distance in a solid | 2. | Angstroms |
(c) | Size of the nucleus | 3. | Light years |
(d) | Wavelength of infrared laser | 4. | Fermi |
|
| 5. | Kilometres |
Codes:
| a | b | c | d |
(1) | 5 | 4 | 2 | 1 |
(2) | 3 | 2 | 4 | 1 |
(3) | 5 | 2 | 4 | 3 |
(4) | 3 | 4 | 1 | 2 |
Answer
2
Question.
Answer
Question.
Answer
Question.From NCERT
Dyne/cm2 is not a unit of :
(1) Pressure
(2) Stress
(3) Strain
(4) Young's modulus
Answer
3
Question.From NCERT PMT - 2000
The units of angular momentum are
(1)
(2)
(3)
(4)
Answer
This product of moment of inertia and angular velocity yields kg⋅m2⋅s−1 or the joule-second.
Ans is 2
Question. From NCERT
The S.I. unit of gravitational potential is
(1) J
(2)
(3)
(4)
.
Answer
The gravitational potential at a point is
the potential energy associated with a unit mass
due to its position in the gravitational field of another body.
Gravitational potential is the amount of work done in bringing a
body of unit mass from infinity to that point.
Gravitational potential (V)
Gravitational potential is a scalar quantity and the
SI unit is .
Question.From NCERT
The unit of L/R is (where L = inductance and R = resistance)
(1) sec
(2) sec–1
(3) Volt
(4) Ampere
Answer
[L/R] is a time constant so its unit is Second.
Question.
SI unit of permittivity is:
(1)
(2)
(3)
(4)