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For class xth physics notes visit

Examsteps “One of the best classes I have ever knew....Keep it up Suman Sir, You are undoubtedly doing your purpose very well to help the students.”

SENDING SOME IMPORTANT QUESTION REGARDING ELECTROSTATICS POTENTIAL AND CAPACITANCE

Class XII Chapter : Electrostatic potential and capacitance Sub:Physics
# Important questions:
1.)Name the physical quantity whose SI unit is J/C. Is it a scalar or a vector quantity?
2.)A point charge Q is placed at point O as shown in the figure. Is the potential difference VA−VB positive, negative or zero, if Q is (a)positive (b)negative? O.Q.-----------------A.-----------------.E
3.)A 500 mC charge is at the center of a square of side 10 cm . Find the work done in moving a charge of 10 mC between two diagonally opposite points on the square.
4.)How much work is done in moving a 500 mC charge between two points on an equipotential surface.
5.)What is the work done in moving a test charge q through a distance of 1cm along the equatorial axis of an electric dipole?
6.)Deduce an expression for the electric potential due to an electric dipole at any point on its axis. Mention one contrasting feature of electric potential of a dipole at a point as compared to that due to a single charge.
7.)Why is the potential inside a hollow spherical charged conductor is constant and has the same value as on its surface?
8.)A hollow metal sphere of radius 5 cm is charged such that potential on its surface is 10 V. What is the potential at the center of the sphere?
9.)A small sphere of radius a carrying a positive charge q, is placed concentrically inside a larger hollow conducting shell of radius b (b> a). This outer shell has charge Q on it . Show that if these spheres are connected by a conducting wire, charge will always flow from the inner sphere to the outer sphere, irrespective of the magnitude of the two charges.
10.)Write two characteristics of equipotential surfaces. Draw the equipotential surfaces due to an electric dipole. [2009,2011 C]
11.)Draw equipotential surface due to a single point charge.
12.)Draw 3 equipotential surfaces corresponding to a field that uniformly increases in magnitude but remains constant along Z- direction. How are constant electric fields along the Z- direction?
13.)Two uniformly large parallel thin plates having charge densities
−σand +σare kept in the X-Z plane at a distance ‘d’ apart. Sketch an equipotential surface due to an electric field between the plates. If a particle of mass m and charge ‘–q’ remains stationary between the plates, what is the magnitude and direction of this field?
14.)Can two equipotential surfaces intersect each other? Give reasons. two charges –q and + q are located at points A (0,0, – a) and B(0,0, +a) respectively. How much work is done in moving a test charge from point P (7,0,0) to Q(–3,0,0)?
15.)Find out the expression for the potential energy of a system of three charges q1, q2and q3 located respectively at r1, r2and r3 with respect to the common origin O
16.)Two point charges 4Q, Q are separated by 1m in air. At what point on the line joining the charges is the electric field intensity zero? Also calculate the electrostatic potential energy of the system of charges, taking the value of charge, Q = 2x10-7C.
17.)Two points charges q1 and q2 initially at infinity, are brought one by one to points p1 and p2 specified by position vectors r1 and r2 , relative to the same origin. What is the potential energy of this charge configuration? Define an equipotential surface. Draw schematically the equipotential surface corresponding to a field that uniformly increases in magnitude but remains constant in direction.
20.) An electric dipole moment P is held in a uniform electric field E.
(a) Prove that no translation force acts on the dipole.
(b) Hence, prove that the torque acting on the dipole is given by pESinθ indicating the direction along which acts.
(c) How much work is required in turning the electric dipole from the position of most stable equilibrium to the position of most unstable equilibrium?

21.) Name the dielectric whose molecules have (i) non- zero and (ii) zero dipole moment.

22.) A metal plate is introduced between the plates of a charged parallel plate capacitor. What is its effect on the capacitance of the capacitor?

23.) Two capacitors of capacitance of 6µf and 12µf are connected in series with a battery. The voltage across the 6µf capacitor is 2 V. Compute the total battery voltage.
29.) The two plates of a parallel plate capacitor are 4 mm apart. A slab of dielectric constant 3 and thickness 3 mm is introduced between the plates with its faces parallel to them. The distance between the plates is so adjusted that the capacitance of the capacitor becomes 2/3rd of its original value. What is the new distance between the plates?

30.) Define the dielectric constant of a medium. Briefly explain the capacitance of a parallel plate capacitor increases, on introducing dielectric medium between the plates.

31.) A parallel plate capacitor is charged to a potential difference V by a DC source. The capacitor is then disconnected from the source. If the distance between the plates is doubled, how will the following changes? (a) Electric field between the plates. (b) Capacitance. (c) Energy stored in the capacitor.

33.) A parallel plate capacitor is charged by a battery to a potential Vo The battery is disconnected and a dielectric slab is inserted to completely fill the space between the plates. How will (i) Its capacitance,
(ii)Electric field between the plates and
(iii) Energy stored in the capacitor will be affected? Justify your answer giving necessary mathematical expressions for each case.
(b) Sketch the pattern of electric field lines due to
(i) A conducting sphere having negative charge on it.
(ii)An electric dipole.

34.) Net capacitance of three identical capacitors in series is 1µf . What will be their net capacitance if connected in parallel? Find the ratio of energy stored in the two configurations if they are both connected to the same source.

MATTER: Anything which has mass and occupies space is called matter. It may be solid, liquid or gas.

TYPES OF MATTER: It is of two types :
1. Pure Substance
2. Impure substance
1. Pure Substance: It may be defined as a material which contains only one kind of atom or molecules.
Pure substance is are of two types:(a) Elements (b) Compounds
(a) Elements:Pure substances which are made up of only one kind of atoms are known as elements.They cannot be split up into two or more simpler substances by any of the usual chemical methods.For example, Iron, gold, silver, carbon, oxygen, nitrogen and sodium etc.
Element is also divided in three categories : (i) Metals, for example: Iron, copper, gold, sodium, silver, mercury, etc.
(ii) Non – metals, for example: Carbon, oxygen, sulphur, nitrogen, oxygen, hydrogen, etc.

(iii) Metalloids : Boron, silicon, germanium, etc.
Properties of Metals: 1.)These are lustrous (shine).
2.) All metals are malleable and ductile.( the property of beating metal into thin sheets is calledMalleability and the property of beating them into thin wires is called ductility)
3.) They are sonorous.(metallic sound when hitted)
4.) All metals are hard except sodium and potassium.
5.) All metals are solids at room temperature except mercury which is a liquid.
Properties of Non-metals: 1.) These are dull in appearance.not shiny
2.) They are poor conductors of heat and electricity except diamond which is a good conductor of heat and graphite which is a good conductor of electricity.
3.) They are neither malleable nor ductile.
4.) They are generally soft except diamond which is the hardest natural substance known.
5.) They may be solids, liquids or gases at room temperature.
Metalloids: The elements that have properties intermediate between those of metals and non-metals, are called metalloids.Ex: Arsenic,boron,Selenium,Antimony etc.
Compounds: It is a form of matter formed by combining two or more elements in a definite ratio by mass.It Can be decomposed into its constituent elements by suitable chemical methods.For example: Water (H2O), oxygen (O2), Nitrogen dioxide (NO2), etc.

Next we come to impure substance.Gives your reviews and comments....🙂🙂🙂

'class ixth cbse "is matter around us pure'