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Statement : The net electric flux through any closed surface is equal to 1/εο times the charge enclosed by the surface.               Φ = q/εο where, q = charge enclosed by the surface PROOF consider, a positive point charge q which is enclosed by an imaginary spherical shell of radius r with 'q' at the centre. ds is a very very small area element of the shell. As we know, the electric field of a positive charge is always radially outward. Pyaare bacchon, agar online study se headache hota hai toh dekh lena, thoda aaram milega tumhe Now, small electric flux through 'ds' is - But, E = q/(4πεο.r²) Therefore, dΦ = [ q/(4πεο.r²) ].ds Now, Net electric flux through the whole spherical surface is - (Integrating both sides and taking limits) Question Find the value of x in the figure if the net flux through the Gaussian surface is '1/2εο' Nm²/C. For "electric field near an uniformly char

Best of Luck STUDENTS Que1. Two small conducting spheres of equal radius have charges 10μC & -20μC respectively placed at a distance R from each other. They experience force F1 . If they are brought in contact and separated to the same distance, they experience force F2 .   Ratio of F1 to F2 is ___ a) 1:2 b) 1:1 c) 2:1 d) 8:1 Pyaare bacchon, agar online study se headache hota hai toh dekh lena, aaram milega Que2. Electric field intensity at a point in between two parallel sheets with like charges of same surface charge densities σ is ___ a) σ/εo b) zero c) σ/2εo d) none of these Que3. There exists an electric field of 2 N/C along y direction. The flux passing through the square of side 1 m placed in xy plane inside the electric field is - a) Zero b) 2 Nm²/C c) 1 Nm²/C d) √3 Nm²/C Que4. A mass of 20g has a charge of 3mC . It moves with a velocity of 20m/s and enters a region of electric field of 80N/C in the same direction as the velocity of the mass. The velocity of t

Consider, an electric dipole of length '2a' having charges '+q' and '-q' placed in an uniform electric field 'E'. The dipole moment 'p' is making an angle 'θ' with the electric field. There are two equal amount of electrostatic forces acting in opposite direction on the dipole which resulting zero net force but a torque 'τ' on the dipole. As, torque = force × perpendicular distance          τ = qE × 2aSinθ For "potential energy of an electric dipole rotated in an uniform electric field" CLICK HERE by      www.advguruji.blogspot.com

Do   your best Q1. If a charged body A having charge +2q touched another uncharged body B . Then A touched another charged body C having charge +2q . Find the force between A and C if they are separated by 1 m. Q2. A system has two charges Q1 = 3μC and Q2 = -3μC . The coordinates of Q1 and Q2 are (10,4,2)m and (5,-9,-10)m respectively. (a) Name the system. (b) Find the net charge of the system. (c) Find the dipole moment of the system. Q3. find the force between the total negative and the total positive charge extracted from 100 ml of water and then kept at 10 cm apart. Q4. Find the nature and magnitude of  x  so that "P" is a null point. Q6. find the amount of two equal charges separated by 10 cm so that the force between them can support the weight of a 40 kg person. ( Take, g = 10 m/s² ) ---------------------------------------------------------------------------------------------- ANSWERS Ans1. , Ans2. , Ans3. (( all questions I have discu

Consider, a short electric dipole having dipole moment p . A point P is at a distance r from the centre O of the dipole such that the angle between p and OP is θ . Now, P act as a point on the axial line for pCosθ component and act as a point on the equatorial line for pSinθ component. The electric fields at point P due to pCosθ and pSinθ are E1 and E2 respectively. Also, they are perpendicular to each other. Now, net electric field at point P is - by www.advguruji.blogspot.com

Consider, an electric dipole of length 2a having charges +q and -q . A point P is lying on the axial line of the dipole at distance r from the centre of the dipole (as shown in figure). The electric fields due to charges -q and +q are E1 and E2 respectively. for Electric field due to an electric dipole on its equatorial line CLICK HERE by     www.advguruji.blogspot.com

Electric dipole If two equal and opposite charges placed at some distance apart. This two charge system is called an electric dipole. Here, '2a' is the dipole length. Note :- Total charge in an electric dipole = -q + q = 0 Electric dipole moment 'p' It is the product of the magnitude of one charge of the dipole and the dipole length. It is a vector quantity directed from negative charge to positive charge. Its SI unit is Cm(coulomb metre). for Electric field due to an electric dipole on its axial line  CLICK HERE   by         www.advguruji.blogspot.com

CHAPTER - 6 NCERT Questions Page 69 Ans1. A group of cells that are similar in structure and work together to do a particular function is called tissue. Ans2. Tissues provide structural strength, mechanical strength, show division of labour for better organisation. Page 74 Ans1. Parenchyma, Collenchyma, sclerenchyma. Ans2. Apical meristem is found at the tip of root or shoot of the plant. Ans3. Sclerenchyma tissue. Ans4. 1. Sieve tubes 2. Phloem fibres 3. Companion cells 4. Phloem parenchyma Page 78 Ans1. Muscular tissue, Nervous tissue. Combination of both of these tissues. Ans2. A neuron consists of a cell body with a nucleus and cytoplasm. Each neuron has a single long part called the axon and many small, short branched parts called dendrite. An individual nerve cell is called neuron, it may be up to a metre long. Ans3. Three features of cardiac muscles are :- 1. They contro

CHAPTER - 5 Ans1. Plant cell 1. It has cell wall. 2. It contain chloroplast. 3. vacuole is large. 4. Nucleus is present in the side of the plant cell. 5. They do not have centriole. Animal cell 1. They don't have a cell wall. 2. They don't contain chloroplast. 3. Vacuole is small. 4. Nucleus is present at the centre. 5. Centriole is present. Ans2. Prokaryotic cell 1. Generally small (1 - 10μm). 2. Nuclear region is poorly defined due to absence of a nuclear membrane known as nucleoid. 3. There is a single chromosome. 4. Membrane bound cell organelles absent. Eukaryotic cell 1. Generally large (5 - 100μm). 2. Nuclear region well defined and surrounded by a nuclear membrane. 3. There are more than one chromosome. 4. Membrane bound cell organelles present. Ans3. If plasma membrane ruptures or breaks down then molecules of some substances will freely move in and out. Ans4. Golgi apparatus has the functio

Chapter - 5 NCERT Class 9th solutions Page 59 Ans1. Robert hooke discovered cells in 1665 while examining a thin slice of cork through a self designed microscope. He saw that the cork resembled the structure of a honeycomb. The small boxes in the comb are called cells. Ans2. A cell is capable of independently carrying out all the necessary activities of life. So, they are called structural and functional unit of life. Page 61 Ans1. Carbon dioxide moves by diffusion and water move by osmosis through cell membrane. Ans2. It is called selectively permeable membrane because it allows the entry and exit of some substances, not all. Page 63 Ans1. (( Pending )) Page 65 Ans1. The two organelles which have their own genetic material are - 1) Mitochondria 2) Plastids Ans2. The cell will not be able to revive and lysosomes will digest it. Ans3. When the cell gets damaged, lysos

Rules concave mirror Rule 1 when light ray is moving parallel to the principal axis towards the mirror, it passes through the principal focus 'F' after reflection. Rule 2 when light ray passes through the principal focus 'F', it goes parallel to the principal axis after reflection. Rule 3 when light ray is incident on the pole of the mirror, it simply reflects from the pole. Rule 4 when light ray passes through the centre of curvature 'C', it bounces back on its initial path. convex mirror Rule 1 when light ray is moving parallel to the principal axis towards the mirror, it goes in opposite direction to the principal focus after reflection. Rule 2 when light ray approaches towards the principal focus, it goes parallel to the principal axis after reflection. Rule 3 (same as concave mirror) Rule 4 when light ray approaches towards the centre of cu

Electric charge It is defined as the fundamental quantity of electricity. Or, It is referred as a particle which experience force when placed in an electric field or when it is moving in a magnetic field. The SI unit of electric charge is coulomb 'C'. Its dimension is 'AT'. It is of two types: Note: In reality, the charge of a down quark is '-e/3' and charge of an upquark is '+2e/3', but they always found in collection and not in singular form. Properties of electric charge 1. Additivity of charge The net charge of any system is the algebraic sum of all the charges present in the system. For example, a body contains charges as shown in figure... 2. Conservation of charge The total charge of any isolated system remains conserved i.e., it can neither be created nor be destroyed but it can only be transferred from one place to another inside the system. For example, when you rub a plasti