The moment of the dipole is directed between -ve charge and + charge. Net force and torque on the system should be zero in equilibrium. Therefore, if Potential Energy is high, the equilibrium will be unstable, and equilibrium will be stable for minimum Potential Energy.

The measure of force which induces an object to rotate around an axis is called the torque. Torque is a quantity of vectors and its path depends on the direction of force on the axis. Torque is given by the formula

→τ=→p×→E

τ = pE sinθ……………………(1)

Potential energy (U) of the system is given as

U = -pE cosθ …………………….(2)

In uniform electric field net force on

(1) Torque can be zero only if θ is 0⁰ or π⁰.

(2) Dipole moment is always zero.

Now let us consider θ = 0 then equation (2) becomes

Potential energy (U) = -pE cos0

U = -pE

Let us consider θ = 180⁰ then equation (2) becomes

U = +pE

∴ PE is high in the case of θ = 180⁰, the equilibrium will be unstable and when θ = 0 then PE is low, so the equilibrium is stable.

Dipole is in constant equilibrium if θ = 0⁰.

A a dipole in stable equilibrium, when Electric filed and dipole moment are perpendicular to each other i.e. the angle between them is zero degree and torque will be maximum.

Given, two current carrying parallel wires,
Distance between the wire , r = 5 cm
Current carried by first wire = 10 A
Current carried by second wire = 5A
Length of the wire, l = 20 cm

The Force between two wires can be found using the formula, 

           

Refractive index of diamond is 2.42 and the critical angle is 24.40 only. The faces of diamond are cut in such a way that a ray of light entering the diamond suffers repeated total internal reflections (angle of incidence is greater than the critical angle) at different faces and remains confined within the diamond. Thus it sparkles.

There are three modes of heat transfer.

1. Conduction: Heat conduction is a process in which heat is transferred from the hotter part to the colder part in a body without involving any actual movement of the molecules of the body. Heat transfer takes place from one molecule to another molecule as a result of the vibratory motion of the molecules. Heat transfer through the process of conduction occurs in substances which are in direct contact with each other. It generally takes place in solids.
2. Convection: In this process, heat is transferred in the liquid and gases from a region of higher temperature to a region of lower temperature. Convection heat transfer occurs partly due to the actual movement of molecules or due to the mass transfer. For example. Heating of milk in a pan.
3. Radiation:  It is the process in which heat is transferred from one body to another body without involving the molecules of the medium. Radiation heat transfer does not depend on the medium. For example: In a microwave, the substances are heated directly without any heating medium.

Let us assume that T>0^∘C 
Heat lost by water= heat gained by ice to melt+ heat gained by water formed from ice
⇒300×1×(50−T)=150×80+150×1×(T−0) 
⇒T=6.7^∘C
⇒T=6.7^∘C
Hence our assumption that T>0^∘C  

An LC circuit, also called a resonant circuit, tank circuit, or tuned circuit, is an electric circuit consisting of an inductor, represented by the letter L, and a capacitor, represented by the letter C, connected together.  Consider a circuit with a capacitor and an inductor, energy taken from the cell and given to capacitor keeps oscillating between L & C. The oscillations between L and C are referred as LC oscillations. ... The capacitor will become fully discharged whereas inductor will be storing all the energy.

The Prism Formula is as follows,

• The surface area of a prism = (2×BaseArea) +Lateral Surface Area
• The volume of a prism =Base Area× Height

Explanation:

Given:

Speed of the electron  m/s

Magnetic Field  T

To find out:

Kinetic Energy of the electron

Solution:

We know that

Mass of an electron  kg

Charge of en electron  C

In magnetic field since the movement of the electron is perpendicular Therefore, the force acting on it will not cause any change in kinetic energy

Thus, kinetic energy is

 Joule

 Joule

 Joule

 eV     (∵ 

 eV

 KeV

On July 7, HRD Minister Ramesh Pokhriyal announced a major CBSE syllabus reduction with 30% of the syllabus slashed for the year 2020-21 for classes 9 to 12 because of the reduction in classroom teaching time due to the Covid-19 pandemic and lockdown.

CBSE has rationalized the syllabus with the help of suggestions from NCERT and the same has been notified by a new CBSE notification as well.

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Current sensitivity : It is defined as the deflection of coil per unit current flowing in it.
Current Sensitivity, 

Voltage sensitivity : It is defined on the deflection of coil per unit potential difference across its ends.

Voltage Sensitivty,  

where G is resistance of galvanometer.
Justification: When number of turns N is doubled, then the current sensitivity (∝ N) is doubled; but at the same time, the resistance of galvanometer coil (G) will also be doubled, so voltage sensitivity (Sv ∝​ N/G) will remain unchanged; hence inreasing current sensitivity does not necessarily increase the voltage sensitivity.  

The current gain in the common-emitter circuit is called Beta (β). Beta is the relationship of collector current (output current) to base current (input current). To calculate beta, use the following formula :

                  β=ΔI_C​​/ΔI_B​

The current gain in the common-base circuit is calculated in a method similar to that of the common emitter except that the input current is I_E​ not I_B​ and the term Alpha (α) is used in place of beta for gain. Alpha is the relationship of collector current (output current) to emitter current (input current). Alpha is calculated using the formula :

α=​ΔI_C​​/ΔI_E

Thus, α=β​/β+1

On July 7, HRD Minister Ramesh Pokhriyal announced a major CBSE syllabus reduction with 30% of the syllabus slashed for the year 2020-21 for classes 9 to 12 because of the reduction in classroom teaching time due to the Covid-19 pandemic and lockdown.

CBSE has rationalized the syllabus with the help of suggestions from NCERT and the same has been notified by a new CBSE notification as well.

Deleted syllabus of CBSE Class 12 Physics

D