ELECTRIC DIPOLE NOTES: ELECTRIC DIPOLE , DIPOLE LENGTH, ELECTRIC FIELD DUE TO ELECTRIC DIPOLE

Electric Dipole: It is a  system of equal and opposite charges separated by some  fixed distance.



DIPOLE LENGTH: the distance AB = 2a is called dipole length. It is a vector quantity , whose direction is from -q to +q. 

Dipole Moment (𝑷⃗  ): It is the measure of strength of electric field produced by a dipole It is defined as the product of magnitude of either charge and separation between the charges. 

i.e. 𝐏⃗ = q × πŸπ’‚⃗  By convention, direction of electric dipole moment is always taken from negative to positive charge. 

Units of 𝑷⃗  : units of 𝑷⃗  = units of charge × units of distance = Cm 

Dimensions of  𝐏⃗  : [𝑷⃗ ] = [q] × [2a] = AT × L = LTA 





ELECTRIC FIELD NOTES : ELECTRIC FIELD

 Electric Field:

 Electric field is a region of space around a charge or a system of charges within which other charged particles experience electrostatic forces.


Electric Field Strength or Electric Field Intensity or Electric Field: 

Electric field strength at a point in an electric field is the electrostatic force per unit positive charge acting on a vanishingly small positive test charge placed at that point.

𝑬 = 𝑭/𝒒₀




The test charge is considered to be vanishingly small  because its presence should not alter the configuration of the source charge and thus the electric field which is intended to be measured.

 Since 𝒒₀ is taken positive, the direction of electric field ( E ) is along the direction of electrostatic force ( F ). 


 Electric field is a vector quantity whose magnitude and direction are uniquely determined at every point in the field. 

SI unit of electric field is newton / coulomb ( NC⁻¹ ).


The electric field produced by a point charge q 

 The magnitude of the force exerted by the charge q on a test charge q₀ is, 




F= `\frac{1}{4 πΡ_{0}}` `\frac{q_{}q_{0}}{r^{2}}`

E= F/q0 =

 F= `\frac{1}{4 πΡ_{0}}` `\frac{q_{}}{r^{2}}`

If q is positive, E is directed away from q. On the other hand, if q is negative, then E is directed towards q. 




ELECTRIC FIELD INTENSITY DUE TO A GROUP OF CHARGES OR SUPERPOSITION PRINCIPLE : 

Electric field intensity at any point due to a group of point charges is equal to the vector sum of electric field intensities due to individual charges at the same point. 



Electric lines of force: 

The paths, along which the unit positive charge will move due to electrostatic force in the field are called electric lines of force. 

The tangent at any point on the electric lines of force gives the direction of electric field at that point.

The properties of electric lines of force are: 

  • i) Electric lines of force start from positive charge and terminate at negative charge. 
  • ii) Electric Lines of force never intersect each other ( see explanation below)
  • iii) Electric lines of force emerge or terminate at right angle to the surface of charge. 
  • iv) ..

 


COULOMB'S LAW : IMPORTANT QUESTIONS

 

Q1  Given two point charges q₁ and q₂ such that q₁q₂ < 0. What is the nature of force between them? 

 Ans. it is possible if  one charge  is  positive and other charge is  negative  in nature. Hence, the force between the two charges will be attractive.


 Q2 Given two point charges q₁ and q₂ such that q₁q₂ > 0.what is the nature of force between the two charges? 



 Ans. As  q₁q₂ > 0  it implies that both the charges are positive in nature. Hence, the force between the two charges will be repulsive.



Q.What is the basic cause of quantisation of charge?

 Ans. During the charging process, only integral number of electrons is transferred from one body to the other. Therefore, charge possessed by a body is always an integral multiple of 1.6 x 10⁻¹⁹ C.

Q. How many electrons are present in one coulomb of charge?
Ans: as we know q =ne
n =q/e
n= 1/1.6 x 10⁻¹⁹ C. =  6.25 x 10¹⁸ 

PHYSICS NOTES: COULOMB'S LAW PART-1

 

Electrostatics: - It is that branch of physics that deals with the charges at rest. ‘Electro’ means study of charges and ‘Static’ means at rest.

 

What is charge? Give types of charges?

Charge: - It is scalar quantity possessed by body by virtue of which the body will show attraction or repulsion on the similar charged bodies.

Types of Charges: - There are two types of Charges Positive charges and Negative charges. Like charges repel each other and unlike attract each other.


What is the cause of charging?

The cause of charging a body is the transfer of electrons from one body to another.

The body which losses electron, becomes positively charged. The body which gains electrons becomes negatively charged.

What is the effect on mass due to charging of a body?

As charging is due to the transfer of electrons. Therefore body which gains electrons becomes negatively charged and its mass increases.

Whereas the body which losses electron becomes positively charged and its mass decreases. This change in mass is negligible as mass of electrons is very small i.e 9.1x 10⁻³¹ kg




What is charging by contact?

Charging by Contact:  When a charged object is touches another object, the other object also gets charged with same polarity due to charge transfer.  This is called charge by contact.

What is charging by Induction? 

When a charged object is brought closer to another object (not touched), the original object doesn’t lose any charge and the other object gets charged as well with opposite polarity. The other extreme end of the newly charged object develops polarity same as that of the charged object. This type of charging is called charge by induction.

Properties of Electric Charge

1. Like charges repel while unlike charges attract each other. The true test of electrification is repulsion and not attraction as attraction may also take place between a charged and an uncharged body and also between two oppositely charged bodies. 

2. Charge is a scalar. ( because charge has only magnitude no direction. 
3. Charge is transferable. 
(Explanation:  When a charged body is put in contact with an uncharged body, the uncharged body becomes charged due to transfer of electrons from one body to the other. If the charged body is positive, it will draw some electrons from the uncharged body and if it is negative then it will transfer some of its excess electrons to the uncharged body) 

4. Charge is always associated with mass: Charge cannot exist without mass though mass can exist without charge. 

5. Charge is Additive. The total charge on a system   can be obtained by algebraically adding all the  charges  present on that system .

π‘ž = π‘ž1 + π‘ž2 + π‘ž3 

For a system containing n  charges , the total charge of the system can be written as, π‘ž = π‘ž1 + π‘ž2 + π‘ž3 + … … + π‘žπ‘›     

6. Electric charge is conserved.   According to the principle of conservation of charges, the charges are neither created nor destroyed; they are only transferred from one body to the other. 



(Explanation: BEFORE RUBBING TOTAL  CHARGE ON BODY A AND B = 0     
after rubbing let 5 electrons transfer from body A to B . Then body B gets -5e charge , then Body will get +5e charge             
                
Total charge after rubbing -5e+ +5e =0) 




7 Electric Charge is quantized.   According to the principle of quantization of electric charge, all the changes on a body  are integral multiples of elementary charge( e) 
 π‘ž = 土 𝑛𝑒 Where n is an integer (zero, a positive or a negative number) and e is the basic unit of charge, that is, the charge carried by an electron or a proton. The value of e is 1.6 × 10⁻¹⁹C 

What is the cause of quantisation? The cause of quantisation is that charging of body is always due to  the transfer of electron in integral number. ( means electrons never transfer in fraction or decimal form.) 

Difference between mass and charge 
Charge :
  • Charge is invariant. It is independent of velocity. 
  • Charge causes electromagnetic force. 
  • Charge is quantised. Q = ne; where n is an integer and e is the charge of one electron. 
  • Charge cannot exist without mass. 
  • Charge can either be positive or negative.  
Mass: 
  • Mass is variant, according to Einstein's equation, when a body is travelling with speed comparable to that of light, its mass changes.
  • Mass causes gravitational force.
  • Mass is not quantised. i.e, mass cannot be expressed as integral multiples of a basic unit. 
  • Mass can exist without charge. 
  • Mass is always positive. 

Coulomb's  Law in electrostatic: 
Coulomb's  Law:  Coulomb's law states that the force of attraction or repulsion between two stationary point changes is directly proportional to the product of the magnitudes of the two charges and inversely proportional to the square of the distance between them. 



F∝ `q_{1}``q_{2}`  ---(1)
F∝ `\frac{1}{r^{2}}` -- (2)
F∝  `q_{1}``q_{2}` `\frac{1}{r^{2}}`

F= K  `q_{1}``q_{2}``\frac{1}{r^{2}}`

Where k is the constant of proportionality and is called force constant. K = `\frac{1}{4 πΡ_{0}}` = 9x10⁹ Nm²C⁻² in SI unit.
F= `\frac{1}{4 πΡ_{0}}` `\frac{q_{1}q_{2}}{r^{2}}`


`{Ξ΅_{0}}` is called absolute permitivity of free space.  
It is equal to 8.854x10⁻¹² farad per meter in free space. 
Unit of permitivity is N⁻¹m⁻²C²
Dimensions of Permittivity: [ M⁻¹ο±£L ⁻³T ⁴A ² ]


Permittivity: 
Permittivity is a measure of how an electric field affects and is affected by a medium.
Limitations of Coulomb's law : It is valid only under the following conditions: - 
1) The electric charges must be at rest. 2) Electric charges must be point charges

Dielectric Constant : The Dielectric constant (K) is defined as  the ratio of the permittivity of the substance to permittivity of the free space (`{Ξ΅_{0}}`). i.e. K = Ξ΅/`{Ξ΅_{0}}` . As Permittivity of medium and permittivity of free space both have same units (F/m i.e. Farad/meter) dielectric constant becomes dimensionless quantity. 

For vacuum or air K = 1 Dielectric constant is also called relative permittivity. Its value is >1 for all media. It is dimensionless quantity. It has no unit.

Coulmb's Law in vector form:

 





As the Colombian forces act along r₁₂ or r₂₁i.e. along the line joining the centers of two charges, so they are central forces.

What is the Principle of Superposition?

The principle of superposition states that every charge in space creates an electric field at point independent of the presence of other charges in that medium. The resultant electric field is a vector sum of the electric field due to individual charges.” 

Continuous Charge Distribution: The continuous distribution of charge may be one dimensional , two dimensional or three dimensional. 
The ways in which charges can be distributed are : 
Linear charge distribution. 
Surface charge distribution. 
Volume charge distribution

Linear charge distribution:  When the charges get distributed uniformly along a length, like around the circumference of a circle or along a straight wire it is called linear charge distribution.



Linear charge density  is defined as charge distributed per unit length, it is  denoted by  Ξ» . 
 Ξ» = q/L 
and it is unit is Coulombs per meter. ( Cm⁻¹)


(b) Surface charge distribution: When the charges get distributed uniformly over the surface , it is called surface  charge distribution.



Surface charge density  is defined as charge distributed per unit area, it is  denoted by  Οƒ . 
Οƒ = q/A  and its unit is Coulombs per meter sqaure. ( Cm⁻²)

Volume charge distribution: When a charge is distributed uniformly over a volume it is said to be volume charge distribution, like distribution of charge inside a sphere, or a cylinder.



  Volume  charge density  is defined as charge distributed per unit volume, it is  denoted by  ρ . 
ρ = q/V  and its unit is Coulombs per meter  cube. ( Cm⁻³). 

10+2 PSEB EXAM : PHYSICS SEPTEMBER SOLVED PAPER

     Time 1.5 hr Class XII 

Sub Physics MM 35 September 2021 

NOTE: 1. Question paper has 35 multiple choice questions.

2. Each question is compulsory. 

3. Q.1 to 11 are knowledge based questions, Q.12 to 24 are understanding based questions & Q.25 to 35 are application based questions.


Q1 The angle between the electric dipole moment (`P⃗` ) and electric field (`E⃗` ) due to the dipole at a point on its axial and equatorial lines respectively are

  • a) `0^{0}` , `180^{0}`
  • b) `90^{0}` , `180^{0}`
  • c) `180^{0}` , `0^{0}`
  • d) `0^{0}` , `90^{0}`

  • a) `0^{0}` , `180^{0}`

Q2 Unit of capacity of conductor is farad. 1 farad(F) is equal to

  • (a)1F = `\frac{1 coloumb}{1ampere}`
  • (b) 1F = `\frac{1 ampere }{1 coloumb}`
  • (c) 1F = `\frac{1 coloumb}{1 vol.t}`
  • (d) 1F = `\frac{1 vol.t}{1 coloumb}`

  • (c) 1F = `\frac{1 coloumb}{1 vol.t}`

Q3 The material of wire of potentiometer is :

  • (a) Copper, because it has high conductivity 
  • (b) Steel, because it is very hard and rust free. 
  • (c) Manganin, because of high resistivity and low temperature coefficient of resistivity. 
  • (d) Aluminium, because it is a good conductor and cheaper than copper

  • (c) Manganin, because of high resistivity and low temperature coefficient of resistivity. 

Q4 A cyclotron cannot be used to accelerate the electrons because

  • (a) Electrons are very heavy and they cannot rotate with the frequency of oscillating electric field. 
  • (b) Electrons are negative charged particles. Therefore, they do not get accelerated inside an electric field. 
  • (c) Electrons are very light particles, they are accelerated at once. They go out of step with oscillating electric field and hence cannot be accelerated. 
  • (d) Electrons mass changes into energy by Einstein formula E = mc2 and therefore they disappear from the system. 

  • (c) Electrons are very light particles, they are accelerated at once. They go out of step with oscillating electric field and hence cannot be accelerated. 

Q5 The angle of dip at the magnetic equator and magnetic poles respectively is

  • a) `0^{0}` , `45^{0}`
  • b) `45^{0}` , `45^{0}`
  • c) `90^{0}` , `0^{0}`
  • d) `0^{0}` , `90^{0}`

  • d) `0^{0}` , `90^{0}`

Q6 Two long parallel wires carrying equal amount of currents in same directions and placed 1m away attract each other with a force of 2 × `10^{-7}` N per meter of their lengths, then current in each wire will be:

  • (a) 0 A 
  • (b) 1A 
  • (c) 2A 
  • (d) 3A

  • (b) 1A 

Q7 The magnetic lines of force around an infinitely long straight current carrying conductor are

  • (a) Concentric circles around conductor 
  • (b) Parallel to length of conductor 
  • (c) Perpendicular to length of conductor 
  • (d) None of these 


  • (a) Concentric circles around conductor

Q8 A metal rod of length 'l' moves with velocity 'v' along the direction of uniform magnetic field `B⃗` , then the motional EMF developed across the ends of the rod is equal to

  • (a) e = B𝑙v 
  • (b) e = 0 
  • (c) e = B𝑙/v 
  • (d) e = Bv/l

  • (a) e = B𝑙v 

Q9. Eddy current may be reduced by using:

  • (a) thick piece of plastic 
  • (b) laminated core of soft iron 
  • (c) thick piece of cobalt 
  • (d) thick piece of nickel 

  • (b) laminated core of soft iron 

Q10 . Effective resistance of an electric circuit to alternating current, arising from combined effect of ohmic resistance and reactance is called:

  • (a) Capacitance 
  • (b) Tolerance 
  • (c) Impedance 
  • (d) Inductance 

  • (c) Impedance 



Q11 Which of the following radiations are used respectively for Lasik eye surgery and to take photograph during the conditions of fog and smoke?

  • (a) Visible rays, X rays 
  • (b) Ultraviolet rays, Infrared rays 
  • (c) Infrared Rays, Ultraviolet rays 
  • (d) Microwaves, Gamma rays 

  • (b) Ultraviolet rays, Infrared rays 

Q12 The equipotential surfaces produced by single positive or negative charge are concentric spheres. The gap between these spheres as we move away from charge

  • (a) decreases 
  • (b) remains same 
  • (c) increases 
  • (d) first increases and then decreases

  • (c) increases 

Q13 If a wire of resistance R and resistivity ρ is stretched to double its length, then its new resistance and resistivity will become

  • (a) 4R, ρ/2 
  • (b) 4R, 4 ρ 
  • (c) 4R, ρ 
  • (d) R/4, 2ρ

  • c) 4R, ρ 

Q14 The sensitivity of a potentiometer can be increased by

  • (a) Increasing length of wire and decreasing resistance in series with the potentiometer wire 
  • (b) Decreasing length of wire and decreasing resistance in series with the potentiometer wire
  • (c) Increasing length of wire and increasing resistance in series with the potentiometer wire 
  • (d) Decreasing length of wire and increasing resistance in series with the potentiometer wire 

  • (c) Increasing length of wire and increasing resistance in series with the potentiometer wire

Q15 . A compass needle does not work at magnetic poles because

  • (a) Compass needle is free to move in a vertical plane only 
  • (b) Compass needle is free to move in a horizontal plane only 
  • (c) Compass needle cannot measure earth magnetic field because it is very weak. 
  • (d) Weight of compass needle becomes more at poles.

  • (b) Compass needle is free to move in a horizontal plane only 

Q16 The resistance of voltmeter, ammeter and galvanometer in the increasing order can be written as

  • (a) Rvoltmeter < Rammeter < Rgalvanometer 
  • (b) Rammeter < Rvoltmeter < Rgalvanometer 
  • (c) Rvoltmeter < Rgalvanometer < Rammeter 
  • (d) Rammeter < Rgalvanometer < Rvoltmeter

  • (d) Rammeter < Rgalvanometer < Rvoltmeter

Q17 The earth’s core has iron but it is not regarded as source of earth’s magnetism because:

  • (a) Iron does not show magnetic properties 
  • (b) Temperature of earth’s core is very high and at this temperature iron does not remain ferromagnetic. 
  • (c) Iron is a superconducting material 
  • (d) None of these


  • (b) Temperature of earth’s core is very high and at this temperature iron does not remain ferromagnetic. 

Q18 Magnetic field due to a current carrying conductor is zero:

  • (a) along a line perpendicular to the wire 
  • (b) along the axial line of the wire 
  • (c) along a line inclined 45° to the wire 
  • (d) it can never be zero

  • (b) along the axial line of the wire 

Q19. A lamp is connected in series with a capacitor to a high frequency AC source. Then it is connected directly to the same source which is true statement about this.

  • (a) Lamp will glow more brightly when the capacitor is in series with it. 
  • (b) Lamp will glow more brightly on connecting it directly to the source. 
  •  (c) Lamp glows with same brightness in both cases. 
  • (d) Brightness of glow of bulb does not depend upon capacitive reactance.  

  • (b) Lamp will glow more brightly on connecting it directly to the source. 

Q20 . The current in series LCR circuit will be maximum when angular frequency Ο‰ is

  • (a) as large as possible 
  • (b) equal to natural frequency of LCR circuit 
  • (c) `(LC)^{1/2}`
  •  (d) 1/LC

  • (b) equal to natural frequency of LCR circuit 


Q21 The current flowing from A to B is increasing as shown in the figure. The direction of the induced current in the loop is

  • (a) clockwise 
  • (b) anticlockwise 
  • (c) straight line 
  • (d) no induced e.m.f. produced

  • (a) clockwise 

Q22 Gamma rays are used in radiation therapy in order to treat cancer because

  • (a) Gamma rays have magical therapeutic properties. 
  • (b) Gamma rays travel faster then other electromagnetic radiations. 
  • (c) Gamma rays are highly energetic and can destroy cancer cells. 
  • (d) None of these

  • (c) Gamma rays are highly energetic and can destroy cancer cells. 

Q23 The equation of electric field part of an electromagnetic wave is given by 𝐄⃗ = [ 3.1 cos { 1.8 y + 5.4 × `10^{6}` t } ] i(unit vector i) , the directions of oscillation of electric field, magnetic field and propagation of wave respectively are

  • (a) x axis, y axis, +z axis 
  • (b) z axis, y axis, +x axis 
  • (c) x axis, z axis, +y axis 
  • (d) x axis, z axis, −y axis 

  • (d) x axis, z axis, −y axis 

Q24 The electromagnetic spectrum in the increasing order of frequency is given as Radio waves, microwaves, Infrared rays, visible rays, Ultraviolet rays, X-rays, Gamma rays. Which physical quantity is same for all these waves in vacuum?

  • (a) wavelength 
  • (b) speed 
  • (c) energy 
  • (d) all of these 

  • (b) speed  

Q25 What capacitance is required to store an energy of 100 KWh at a potential difference of `10^{4}` V?

  • a) 9.2 F 
  • b) 3.7 F 
  • c) 7.2 F 
  • d) 2.7F 

  • c) 7.2 F

Q26 Two similar capacitors of capacity C each are first connected in series and then in parallel. The ratio of the net capacity obtained in the two cases is

  • (a) 4 
  • (b) 1/4 
  • (c) 1 
  • (d) 2

  • (b) 1/4 

Q27 The resistances of two bulbs at the same voltage are in the ratio 1:2. On connecting them in parallel, the power consumption will be in the ratio

  • (a) 2:1 
  • (b) 1:1 
  • (c) 1:4 
  • (d) 1:2


  • (a) 2:1 

Q28 A Galvanometer of resistance 12 ohm gives full deflection for 8 mA. It can be converted into voltmeter of range 0-32 V with help of resistance of:

  • (a) 5988 ohm 
  • (b) 3988 ohm
  • (c) 2500 ohm 
  • (d) 4000 ohm

  • (b) 3988 ohm

Q29. In the magnetic meridian of a certain place, the horizontal component of earth’s magnetic field is 0.26 G and the dip angle is `60^{0}` , the vertical component of earth’s magnetic field at that place will be (G → gauss)

  • (a) `\frac{0.26}{\sqrt{3}}`G
  • (b) `\sqrt{3}`G
  • (c) 0.52 G 
  • (d) 0.13 G

  • (b) `\sqrt{3}`G

Q30 . Magnetic susceptibility of magnesium at 300K of temperature is 1.2 × `10^{-5}` , the magnetic susceptibility of magnesium at 30K of temperature will be

  • (a) 1.2 × `10^{-3}`
  • (b) 1.2 × `10^{-4}`
  • (c) 1.2 × `10^{-5}`
  • (d) 1.2 × `10^{-6}`

  • (b) 1.2 × `10^{-4}`

Q31 The smallest value of magnetic dipole moment  𝝁l  of an atom due to orbital motion of an electron in first orbit is called Bohr Magneton πœ‡B. The value of Bohr Magneton is equal to

  • a) πB=9.27x `10^{-24}`A`m^{2}`
  • b) πB=1.38x `10^{-23}`A`m^{2}`
  • c) πB=6.022x `10^{23}`A`m^{2}`
  • d) πB=1.6x `10^{-19}`A`m^{2}`

  • a) πB=9.27x `10^{-24}`A`m^{2}

Q32 The magnetic flux passing through a coil changes from 6×`10^{-3}` Wb to 7.2×`10^{-3}` Wb in 0.02s.Calculate the induced e.m.f.:

  • (a) -6×`10^{-2}`V
  • (b) 8×`10^{-2}`V
  • (c) 2×`10^{-2}`V
  • (d) -3×`10^{-2}`V

  • (a) -6×`10^{-2}`V

Q33 How much current is drawn by the primary coil of a transformer connected to 220V supply, when it delivers power to a 110V and 550 W refrigerator?

  • (a) 0.5 A 
  • (b) 2.5 A 
  • (c) 5 A 
  • (d) 1.5 A

  • (b) 2.5 A 

Q34 An inductor of 1 H and negligible resistance is used on the mains of frequency 50 Hz. Find the reactance of the inductor

  • (a) 50 Ο€ H 
  • (b) 100 Ο€ H 
  • (c) 75 Ο€ H 
  • (d) 60 Ο€ H

  • (b) 100 Ο€ H 

Q35 Find the wavelength of electromagnetic waves of frequency 6×`10^{12}` Hz in free space having speed of 3 × `10^{8}` m/s in free space

  • a) 6 x `10^{-5}` 
  • b) 5 x `10^{-5}` 
  • c) 2.5 x `10^{-5}` 
  • d) 1.5 x `10^{-5}` 

  • b) 5 x `10^{-5}` 


SOLVED 10+1 PHYSICS SEPTEMBER QUESTION PAPER

 

Q1 The definition of one atomic mass unit and its value is

  • (a) 1/12th the mass of an atom of oxygen-16, 1amu = 1.6 × `10^{-19}` Kg 
  • (b) 1/16th the mass of an atom of carbon-12, 1amu = 9.1 × `10^{-31}` Kg 
  • (c) 1/12th the mass of an atom of carbon-12, 1amu = 1.66 × `10^{-27}`Kg 
  • (d) The mass of helium nucleus, 1amu = 3.2 × `10^{-27}` Kg 

  • (c) 1/12th the mass of an atom of carbon-12, 1amu = 1.66 × `10^{-27}`Kg 

Q2  Which of the following quantity is vector quantity?

  • (a) Density 
  • (b) angular velocity 
  • (c) Energy 
  • (d) angular frequency

  • (b) angular velocity 

Q3  Which of the following quantities remains constant in a projectile motion?

  • (a) Speed of body 
  • (b) acceleration acting on the body 
  • (c) vertical component of velocity 
  • (d) linear momentum of body

  • (b) acceleration acting on the body 

Q4 The working of rocket is based on the principle of

  • (a) Newton's first law 
  • (b) inertia of rest 
  • (c) conservation of linear momentum 
  • (d) none of these

  • (c) conservation of linear momentum 

Q5  The component of contact force in the direction parallel to the surface of contact of two bodies and perpendicular to the surface are called

  • (a) normal reaction, frictional force 
  • (b) frictional force, normal reaction 
  • (c) centripetal force, centrifugal force 
  • (d) centrifugal force, centripetal force 

  • (b) frictional force, normal reaction 

Q6 A car accelerates on a horizontal road due to the force exerted by

  • (a) the engine of the car 
  • (b) the driver of the car 
  • (c) the earth gravitational force 
  • (d) the friction between tyres and road

  • (d) the friction between tyres and road

Q7  A body of certain mass is lifted upwards from ground to a certain height, the work done by the gravitational force and applied force respectively are

  • (a) positive, negative 
  • (b) negative, positive 
  • (c) positive, positive 
  • (d) negative, negative


  • (b) negative, positive 

Q8 The value of coefficient of restitution e for elastic and perfectly inelastic collisions are respectively

  • (a) 0,1 
  • (b) 0,0 
  • (c) 1,1 
  • (d) 1,0

  • (d) 1,0

Q9.  The center of mass of two non identical particle system

  • (a) always lies in between two particles and on the line joining them 
  • (b) always lies at the center of two particles 
  • (c) may lie outside the two particle system but on the line joining them 
  • (d) always lies nearer the lighter particle

  • (a) always lies in between two particles and on the line joining them 

Q10 Angular momentum has the same unit as

  • (a) Impulse × distance 
  • (b) Linear momentum × time 
  • (c) Work × frequency 
  • (d) Power × distance

  • (a) Impulse × distance 

 

Q11 In the absence of external torque acting on a rotating body, which of the following quantities can change?

  • (a) Angular momentum 
  • (b) Angular velocity but not moment of inertia 
  • (c) Moment of inertia but not angular velocity 
  • (d) Both angular velocity and moment of inertia 

  • (d) Both angular velocity and moment of inertia 

Q12  The Vander Wall’s equation for an ideal gas is given by (P + a/`V^{2}` )(V- b) = RT, where P = pressure, V = volume, T = temperature, R = universal gas constant, a and b are constants. The dimensions of a and b in this equation are

  • (a) [a] = `L^{3}`  [b], M`L^{5}` `T^{-2}` 
  • (b) [a] = `L^{3}`  [b], M`L^{-3}` `T^{-2}` 
  • (c) [a] = M`L^{5}` `T^{-2}`  [b] = `L^{3}`
  • (d) [a] = M`L^{3}` `T^{-2}`  [b] = `L^{5}`

  • (b) [a] = M`L^{5}` `T^{-2}`  [b] = `L^{3}`

Q13  . A person starts his journey from his home at 9.00 a.m.to his office and came back to his home at 5.00 p.m. His office is 20 km from his home, then the displacement and distance covered in his complete journey are:

  • (a) 20 km, 0 Km 
  • (b) 0 km, 20 Km 
  • (c) 40 km, 0 Km 
  • (d) 0 km, 40 Km

  • (d) 0 km, 40 Km

Q14 Which of the following statement for an object in uniform motion is not true?

  • (a)The object must be moving in straight path along same direction
    (b) The object covers equal displacements in equal intervals of time 
  • (c) The velocity of object changes by equal amounts in equal intervals of time like free fall under gravity. 
  • (d) The acceleration of object must be zero

  • (c) conservation of linear momentum 

Q15  When a car moving in a fixed direction accelerates

  • (a) The frictional force acts on it in the direction opposite to the direction of motion
  • (b) The frictional force acts on it in the same direction as direction of motion 
  • (c) Frictional force is not required. The engine of the car gives the force needed. 
  • d) No force is required due to inertia of motion. The car accelerates by itself

  • (b) The frictional force acts on it in the same direction as direction of motion 

Q16 If a body is stationary then

  • (a) there is no force acting on it 
  • (b) the forces acting on it are not in contact with it 
  • (c) the combination of forces acting on it balance out 
  • (d) the body is in vacuum

  • (c) the combination of forces acting on it balance out 

Q17  The restoring force produced in a spring is a conservative force. It means

  • (a) Work done by spring force depends only on the initial and final positions. 
  • (b) Work done by spring force depends on the path between initial and final positions. 
  • (c) Work done by spring force in a cyclic process is non zero. 
  • (d) This statement is false. Spring force is a non conservative force


  • (b) Work done by spring force depends on the path between initial and final positions.

Q8 A man pushes a wall normally and fails to displace it but himself gets displaced by 2 m away from wall against frictional force between his feet and ground. Work done by wall on him is:

  • (a) zero
  • (b) negative 
  • (c) positive 
  • (d) depends on the frictional force between the wall and hands of the

  • (c) positive 

Q19.  Four particles given below have same linear momentum, which has maximum kinetic energy?

  • (a) proton 
  • (b) electron 
  • (c) deutron 
  • (d) alpha particle

  • (b) electron 

Q20 In which of the following motions momentum changes but K.E. does not change?

  • (a) A freely falling body 
  • (b) A body moving in uniform motion 
  • (c) A body vertically thrown upwards 
  • (d) A body moving in uniform circular motion 

  • (d) A body moving in uniform circular motion 

 

Q21 The casing of a rocket in flight burns up due to friction. At whose expense is the heat energy required for burning obtained?

  • (a) The kinetic energy of rocket 
  • (b) Energy given by atmosphere 
  • (c) Energy given by burning fuel 
  • (d) The potential energy of the rocket 

  • (a) The kinetic energy of rocket 

Q22  When perfectly inelastic collision between two objects takes place, then during the collision

  • (a) Linear momentum remains conserved.
    (b) Kinetic energy remains conserved. 
  • (c) Both kinetic energy and linear momentum remain conserved. 
  • (d) Neither kinetic energy nor linear momentum remains conserved.

  • (a) Linear momentum remains conserved. 

Q23  The angular velocity of a planet revolving in an elliptical orbit around the sun increases, when it comes near the sun and vice-versa. This process better explained on the basis of law of conservation of:

  • (a) Mass 
  • (b) Linear Momentum 
  • (c) Angular Momentum 
  • (d) Energy 

  • (c) Angular Momentum 

Q24 A cylinder rolls down an inclined plane without slipping as shown. The work done against friction during rolling motion is

  • (a) always positive 
  • (b) always negative 
  • (c) zero 
  • (d) first positive and then negative

  • (c) zero 

Q25   The temperatures of two bodies measured by a thermometer are t1 = 20`0^{C}` ± 0.5`0^{C}` and t2 = 50`0^{C}` ± 0.5`0^{C}`. The temperature difference t = t2 – t1 between them is given by

  • (a) t = 30 `0^{C}` ± 0.5 `0^{C}`
  • (b) t = 70 `0^{C}`± 0.5 `0^{C}`
  • (c) t = 70`0^{C}`± 1.0`0^{C}`
  • (d) t = 30`0^{C}`± 1.0`0^{C}`

  • (d) t = 30oC ± 1.0oC

Q26 In the experiment of finding the reaction time of Sunil, his friend releases a scale from rest in between the fingers of Sunil and notices the scale to fall by a distance of 20 cm before being held by Sunil. The reaction time of Sunil is (Use g = 10 ms-2 )

  • a) 0.1s 
  • (b) 0.2s 
  • (c) 0.3s 
  • (d) 0.4s

  • (b) 0.2s 

Q27 The angle made by vector 𝐴⃗⃗ = 2𝑖̂+ 𝑗̂ with x axis is

  • (a) tanΞΈ = 0.5 
  • (b) tanΞΈ = 2 
  • (c) tanΞΈ = √5 
  • (d) tanΞΈ = √ 2/5


  • (a) tanΞΈ = 0.5 

Q28 At what angle to the horizontal should an object be projected so that the maximum height reached is equal to the horizontal range?

  • (a) tan ΞΈ = 1/4 
  • (b) tan ΞΈ = 1/2 
  • (c) tan ΞΈ = 4 
  • (d) tan ΞΈ = 2 

  • (c) tan ΞΈ = 4 

Q29.  A rocket with a lift – off mass 3.5×`10^{4}` kg is blasted upwards with an initial acceleration of 10 m`s^{-2}` . Then, the initial thurst of the blast

  • (a) 3.5×`10^{5}` N 
  • (b) 7.0×`10^{5}` N 
  • (c) 14.0×`10^{5}` N 
  • (d)1.75×`10^{5}`N

  • (b) 7.0×`10^{5}` N 

Q30 Determine the maximum acceleration of the train in which a box lying on its floor will remain stationary. Given that the coefficient of static friction between the box and train’s floor is 0.15. Take g = 10m`s^{-2}`

  • (a) 0.5 m`s^{-2}`
  • (b) 1.0 m`s^{-2}`
  • (c) 2.5 m`s^{-2}`
  • (d) 1.5 m`s^{-2}`

  • (d) 1.5 m`s^{-2}` 

 

Q31 A police officer fires a bullet of mass 50.0 g with speed 200 m`s^{-1}`  on soft plywood of some thickness. The bullet emerges with speed 100 m`s^{-1}` from other side. Using work energy theorem, find the work done by plywood in reducing the speed of bullet?

  • (a) – 50 J 
  • (b) – 550 J 
  • (c) – 750 J 
  • (d) – 200 J

  • (c) – 750 J 

Q32  A particle of mass M is moving in a horizontal circle of radius R with uniform speed v. When it moves from one point to a diametrically opposite point, it’s

  • (a) K.E changes by `\frac{1}{2}mv^{2}`
  • (b) linear momentum does not change 
  • (c) linear momentum changes by 2 M v 
  • (d) K.E changes by `mv^{2}`

  • (c) linear momentum changes by 2 M v 

Q33  How much energy is released, when 1mg of uranium is completely destroyed in an atom bomb.

  •  (a) 7×`10^{10}` J
  • (b) 8×`10^{10}` J
  • (c) 9×`10^{10}` J
  • (d) 5×`10^{10}` J 

  • (c) 9× `10^{10}` J

Q34 A solid cylinder of moment of inertia 0.625 kg `m^{2}`  rotates about its axis with angular speed 100 rad`s^{-1}`. What is the magnitude of angular momentum of the cylinder about its axis?

  • (a) 62.5 kg`m^{2}s^{-1}`
  • (b) 625×104 kg`m^{2}s^{-1}`
  • (c) 6.25 kg`m^{2}s^{-1}` 
  • (d) 625×105kg`m^{2}s^{-1}`

  • (a) 62.5 kg`m^{2}s^{-1}`

Q35  The sun rotates around itself in 27 days, if it were to expand to twice its present diameter, what would be its new period of revolution?

  • (a) 27 days 
  • (b) 54 days 
  • (c) 81 days 
  • (d) 108 days

  • (d) 108 days


Current Electricity : MCQ on Current Electricity

The branch of Physics, which deals with the study of charges in motion is called Current Electricity.

Electric Current :- It is defined as the rate of flow of charge across any cross-section of conductor.

If a charge ‘q’ flows across any cross-section in ‘t’ second ,current ‘i’ is given by I= q/t

I= ne/t


Q1 S.I Unit of Electric motive force is 

  • Coulomb 
  • Ampere
  • Volt 
  • Coulomb/Ampere

  • Volt 

Q2 Electromotive force .............potential difference.

  • may be equals to 
  • may be greater than
  • both (a) and (b) 
  • none of these

both (a) and (b)


Q3 A wire is carrying a current. Is it charged?

  • Yes, 
  • No

No 

(Electric current is the flow of free electrons in the conductors. At any instant, the no. of electrons leaving the wire is always equal to the no. of electrons flowing from the battery into it. Hence the net charge on the wire is zero.)

Q4 Electric current is a .................. quantity.

  • Scalar
  • Vector
  • Tensor
  • None of the above

  • Scalar 


Q5 S.I Unit of Electric current is ... 

  • Coulomb 
  • Ampere
  • Tesla 
  • Coulomb/Ampere

  • Ampere


Q6 One Ampere =.................................... stat ampere.

  • 3x`10^{19}`
  • 3x`10^{9}`
  • 2.25x `10^{19}`
  • None of these 

  • 3x`10^{19}`


Q7 How many electrons passes in one second when current is 1A. 

  • 5.26 × `10^{18}`
  • 6.25 × `10^{25}`
  • 5.26 × `10^{19}`
  • 6.25 × `10^{19}`

  • 6.25 × `10^{25}`

 


Q8 The relaxation time in conductors:

  • Increases with increase in temperature
  • Decreases with the increases of temperature
  • It does not depend on temperature
  • Changes suddenly at 400 Kelvin.

  • Decreases with the increases of temperature.


Q9 According to Ohm’s Law 

  • V is directly proportional to I
  • V is inversely proportional to I
  • V is directly proportional to √I
  • All of the above.

  • V is directly proportional to I


Q10 Ohm's law is applicable to

  • Semiconductors
  • Vacuum tubes
  • Carbon resistors
  • None of these

  • None of these

PRACTICE MORE MCQ 10+2 Physics for all Exams click here

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