12th Class Physics Chapter 1 Short Questions with Answers Solved

Question: 1

Electric lines of force never cross why?

Answer: 1

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Electric lines of force never cross each other,This is because that electric field line has only one direction at any given point.If the lines cross ,electric field lines could have more than one direction which is not possible.

Question: 2

If a point charge q of mass is released in a non-uniform electric field with field lines pointing in the same directions,will it make rectilinear motion?

Answer: 2

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If a point charge q of mass m is placed at any point in the field ,it will follow straight or rectilinear path along the field line due to repulsive force.

Question: 3

A point charge move rectilinear path in an electric field.Explain.

Answer: 3

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If a point charge q of mass m is placed at any point in the field in the point,it will follow straight or rectilinear path along the field line due to repulsive force.

Question: 4

Describe the force on positive charge when placed between parallel plates with opposite and equal charges.

Answer: 4

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When a positive point charge is placed between parallel plates with opposite but equal amount of charge ,then electric field intensity due to one plate is equal in magnitude but in same direction of the electric field intensity due to the other plate.So the value of resultant electric field intensity is non-zero.Hence the point charge will be accelerated towards negative plate.

Question: 5

What is the effect of medium between the charges upon coulomb's force?

Answer: 5

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.If an insulating material i.e direction is places between the charges ,it will reduce the electrostatic force as compared to free space by factor called relative permittivity.

Question: 6

Define electric flux.Write its SI units.

Answer: 6

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The number of the field lines passing through a certain element of area is known as electric flux through that area.Its SI units is Nm²C^-1.

Question: 7

State coulomb's law.

Answer: 7

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It states that the force of attraction or repulsion between two point charges is directly proportional to the product of the magnitudes of charge and inversely proportional to the square of the distance between them.

Question: 8

Define Time constant for RC Circuit.

Answer: 8

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The time required by the capacitor to deposit 0.63 times the equilibrium charge q is called time constant.The product of R and C has the dimensions of time.So this product is known as time constant.

t=RC

Question: 9

Distinguished between electric field and field intensity.

Answer: 9

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Electric Field: The space or region around the charge in which it exerts its electric force on other charges is called electric field.

Question: 10

Define electric intensity and give its unit.

Answer: 10

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The electrostatic force per unit test charge,at a specific point in the electric field is called electric field intensity.Its unit is NC^-1.

Question: 11

Suggest a method 'shield' an apparatus from electric field even when it is to be kept in the region where electric field is present.

Answer: 11

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An apparatus will be shielded from electric field when it is kept inside the metallic box,so that the charge will only reside on the outer surface of the container.It is in accordance with Gauss law.

Question: 12

Describe the force or forces on a positive point charge when placed between parallel plate,with similar and equal charges.

Answer: 12

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When a positive point charge is placed between parallel plates with similar and equal charges,then the electric field intensity due to one plate is equal in magnitude but opposite in direction of electric intensity due to other plate.So the value of resultant electric field intensity E is zero,Hence the net force on the positive charge is zero,Thus is will remain at rest.

Question: 13

Write two properties of electric field.

Answer: 13

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1.Electric field line originate from positive charge and end om negative charges.

2.The tangent to a field line at any point gives the direction of the electric field intensity at the point.

Question: 14

What is Potential Gradient?

Answer: 14

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The quantity gives the maximum value of rate of change of electric potential in magnitude and direction with respect to distance,It is known as potential gradient.

Question: 15

Is E is necessary zero inside a charged rubber balloon if balloon is spherical?

Answer: 15

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Yes, E is necessarily zero inside a charged rubber balloon if balloon is spherical.

Question: 16

Give the statement of Gauss's law.

Answer: 16

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It states that the total electric flux through any closed surface is equal to 1/e_otimes the total charged encloses in it.

Question: 17

What is strength of electric field inside a hollow charged sphere and why?

Answer: 17

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The strength of electric field inside a hollow charge is zero.inside a hollow charge sphere q=0.

Question: 18

Why do the electrons tend to go to region of high potential?

Answer: 18

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We know that the electrons are negatively charged particles.So,when they are put inside an electric field they tend to go the region of high potential from the region of low potential.

Question: 19

Is it true that Gauss's law states that the total number of lines of forces crossing any closed surface in the outwards direction is proportional to the net positive charged enclosed within surface?

Answer: 19

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Yes the above statement is true,The total number of lines of force crossing any close surface in the outwards directions means electric flux.

Question: 20

What is electric potential energy and electric potential difference?

Answer: 20

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Electric potential energy: The energy is acquired by unit positive charge in carrying it from one point to the other against the electric field keeping it in electrostatic equilibrium is called as electric potential energy,It is the energy stored in the charge 'q' because of its position in an electric field.It is measured in joules.

Question: 21

Define electric potential and give its SI units.

Answer: 21

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The electric potential at any point in an electric field is equal to work done in bringing a unit positive charge from infinity to that point keeping it in equilibrium.Its SI unit is Volt (V).

Question: 22

Do electrons tend to go region of high potential or low potential?

Answer: 22

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Electrons tend to go to a region of high potential from low potential because electrons are negatively charged.

Question: 23

How can you identify that which plate of a capacitor is positively charged?

Answer: 23

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Gold leaf electroscope is used,To check the polarity,disc of positively charged electroscope is brought close to the capacitor plate.If the divergence of gold leaves increases;the plate is positively charged and vice versa.

Question: 24

What is photoconductor?

Answer: 24

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A material which behaves as an insulator when it is in dark and becomes conductor when it is exposed to light is known as photoconductor.

Question: 25

Does the total flux depend upon the shape or geometry of the closed surface?

Answer: 25

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No,the total flux does not depend upon the shape or geometry of the closed surface,It depends upon medium and charge enclosed.

Question: 26

How sharks looks their prey?

Answer: 26

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Sharks have special organs,called the ampullae of Lorenzini that are very sensitive to electric field and can detect potential difference of the order of nano volt and can locate their prey very precisely.

Question: 27

What is meant by EEG and ERG?

Answer: 27

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Electroencephalography: is usually applied over human brain to check its abnormal behaviour by the use of electrical energy.For this electrodes are connected to the selected portion of the head and the corresponding response is seen graphically through the screen of a recording device.

Question: 28

Center of planetary system is oppositely charged to the rest of planets.How orbits of planets would be modified?

Answer: 28

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It would add or subtract the gravitational force if the charge was ;large enough and the sun was charged.So the radius of the orbits would be changed

Question: 29

Define electrostatics and electric force,

Answer: 29

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Electrostatics: The branch of physics which deals with the study of stationary charges is called electrostatics.Electric force: The force which holds the negative and positive charges that make up atoms or molecule is called electric force.

Question: 30

What is capacitor?Define the capacitance.

Answer: 30

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Capacitor is a device used to store charge,

Capacitance is a measure of ability of capacitor to store charge.

Question: 31

Define electron volt.

Answer: 31

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It is defined as The amount of energy acquired or lost by an electron when it is displaced across two points having potential difference of one volt.It is measure on electrons volts.

Question: 32

Define xerography and photoconductor.

Answer: 32

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Xerograph is a photocopying process,It is taken from the Greek word "xeros" and "graphos" when mean dry writing.

Photoconductor is an insulator in the dark and becomes a conductor when exposed to light.

Question: 33

How can you identify that when plate of capacitor is positively charged?

Answer: 33

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For the identification of positively charged plate of a capacitor golf leaf electroscope is used,For this purpose the plate of capacitor is brought near the positively charged disc of electroscope.If the divergence of the gold leaves increase then the capacitor will be positively charged and vice versa.

Question: 34

What is time constant?

Answer: 34

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The time required by the capacitor to deposit 0.63 times the equilibrium charge qois called time constant.The product of R and C has the dimensions of time So,this product is known as time constant.

Question: 35

What depend on the slow or fast charging and discharging of a capacitor?

Answer: 35

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How fast or how slow the capacitor is charging or discharging depends upon the products of the resistance and the capacitance called time constant.Capacitor is charged or discharged rapidly when RC is small.

Question: 36

Write down two difference between electric and gravitational force.

Answer: 36

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Differences:Electrical force is might be attractive as well as repulsive while the gravitational force is only attractive.Electrostatics force is medium dependent while the gravitational force is not.

Question: 37

Define electric polarization and electric dipole.

Answer: 37

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When dielectric is placed between the plants of capacitor,positive and negative charge of its molecules displace from their position.Positive charges are attracted towards negative plates and negative charges towards positive plate,dipoles are formed.This process is called polarization.

Two equal and opposite charges separated by a small distance is called dipole.

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12th Class Chapter 1 Physics Short Questions

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