unit and dimensions pdf
Unit and dimensions class 11
In this post we have to study about a very important chapter unit and dimension in physics and unit and dimension Notes and also see the unit and dimension formula for jee main and also for class 11th . If you find any error in this post then feel free to contact us our team solve that minor issue.if you want to see Unit and dimension in hindi then change the Google translate laungauge below
Unit and dimension Notes class 11th
Unit : In order to measure a physical quantity a "standard" is required : this "standard" is called unit of that physical quantity
The magnitude M of a physical quantity = NU, where
• N= Numercial value of the quantity and
• U = unit of the quantity
Fundamental and Derived Units : The unit of length, mass and time are taken as fundamental units, the units of other quantities which are derived from it are called derived units.
System of Units : There are four systems of units to measure a Physical quantity
(a) C. G. S. System : In this system the units of length, mass and time are respectively cm, gram and second.
(b) F. P. S. System : The Units of length, mass and time are known as foot, pound and second.
(c) M. K. S. System : Units of length, mass and time are respectively metre, kilogram and second.
(d) S. I. Units (International System of Units) :
There are seven basic units namely,
1. Metre for length
2. Kilogram for mass
3 Second for time
4. Kelvin (K) for temperature
5. Ampere (A) for current
6. Candela for luminous intensity
7. Mole for amount of substance.
There are two supplementary S. L. Units.
1. Radian for plane angle
2. Steradian for solid angle
Unit of angle : Radian and degree are the units of angle.
2π radian = 360⁰
Dimension : In order to obtain the unit of a physical quantity, the fundamental units are raised by powers, which represents its dimension.
For example if we write, [Y] = [Mᵃ Lᵇ Tᶜ] then a, b and e are respectively dimension of Y in M, L and in T.
Dimensionless quantity : In the equation [Y] = [Mᵃ Lᵇ Tᶜ]. if a =b=c=0, then the quantity is called dimensionless. As for example,
(a) Strain, specific gravity, angle. They are ratio of two similar quantities
(b) Number, such as 9, 1/4sin, etc.
A dimensionless quantity has same numerical value in all
Dimensional equation : It is an equation which represents involvement of the fundamental units in a physical quantity,
as for example, Force [M L T⁻²)
Use of dimensional equation : To change the value of a physical quantity from one system to another
N₁ U₁ = N₂ U₂ ,
(b) To check the accuracy of an equation
It is based on principle of homogencity.
(c) To establish an equation.
Significant figure : It may be defined as that figure in a given number which can be relied.
Percentage error : If dy is the error in the measurement of a quantity, then percentage error is
dy/y×100%
Q. What are the unit of measurement ?
Ans 👉 There are seven unit of measurement
(1) the kilogram (kg),
(2) the second (s),
(3) the kelvin (K),
(4) the ampere (A),
(5) the mole (mol),
(6) the candela (cd),
(7) the meter (m),
Q. SI unit and dimensions of magnetic moment ?
Ans 👉
Q. what is the unit of compressibility ?
Ans 👉 m^(2/n)
Q. state the si unit and dimensions of magnetic flux ?
Ans👉 si unit = (Wb)
Dimensions = ML2T-2I-1]
Unit and dimension jee main question or unit and dimension question
1. Write down the dimenional formula of impulse
Ans. [M L T⁻¹ ]
Impulse force x time= [MLT⁻²}× [T] = [MLT⁻¹] =
2. Write down the dimension of Boltzmann's Constant ?
Ans. [M L² T⁻² K⁻¹ ]
3. Write down the dimension of universal gas constant ?
Ans. [M L² T⁻² K¹ ].
4. Write down the dimension of coefficient of viscosity (m).
Ans. [M L⁻¹ T⁻¹ ]
5. Write down the dimension of Gravitational Constant
Ans. [M⁰ L⁰ T]
6. If L and C represents the inductance and capacity, then write down the dimension of LC.
Ans. [M⁰ L⁰ T² ]
7. If a current I is flowing through an inductance L, then find the dimension of LI²
Ans. [M L² T⁻² ]
8. If C represents the capacity of a condenser and if V represents the P.d. across its end then find the dimension of CV2.
Ans. [M L² T⁻² ]
9. What is the dimension of surface tension ?
Ans. [M T⁻²]
10. Write down the dimension of €₀
Ans. [M⁻¹ L⁻³ T⁴ A²]
11. Write down the dimension of Resistance, R.
Ans. (M L² T⁻³ A⁻²]
12. Write down the dimension of 1/√(u₀€₀)
Ans. [Mº L T⁻¹ A⁰]
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