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All questions of September Week 4 for NEET Exam
A flux of 1m Wb passes through a strip having an area A = 0.02 m2. The plane of the strip is at an angle of 60º to the direction of a uniform field B. The value of B is
- a)0.1 T
- b)0.058 T
- c)4.0 mT
- d)none of the above
Correct answer is option 'B'. Can you explain this answer?
A flux of 1m Wb passes through a strip having an area A = 0.02 m2. The plane of the strip is at an angle of 60º to the direction of a uniform field B. The value of B is
a)
0.1 T
b)
0.058 T
c)
4.0 mT
d)
none of the above
|
Mira Joshi answered |
formula of flux is = BAcosθ
θ is angle between A and B
θ=30∘
ϕ=1×10−3wb
A=0.02 m2
angle between screen and B is 60∘
B = ϕ/acos30 = 10-3/ 2 x 10-2 x cos√3/2 = 0.058T
In the arrangement shown in given figure current from A to B is increasing in magnitude. Induced current in the loop will
- a)have clockwise direction
- b)have anticlockwise direction
- c)be zero
- d)oscillate between clockwise and anticlockwise
Correct answer is option 'A'. Can you explain this answer?
In the arrangement shown in given figure current from A to B is increasing in magnitude. Induced current in the loop will
a)
have clockwise direction
b)
have anticlockwise direction
c)
be zero
d)
oscillate between clockwise and anticlockwise
|
New Words answered |
The direction of the induced current is as shown in the figure, according to Lenz’s law which states that the indeed current flows always in such a direction as to oppose the change which is giving rise to it.
A conducting square loop of side I and resistance R moves in its plane with a uniform velocity v perpendicular to one of its sides. A uniform and constant magnetic field B exists along the perpendicular to the plane of the loop in fig. The current induced in the loop is
- a)RvB
- b)zero
- c)vBL/R
- d)vBL
Correct answer is option 'B'. Can you explain this answer?
A conducting square loop of side I and resistance R moves in its plane with a uniform velocity v perpendicular to one of its sides. A uniform and constant magnetic field B exists along the perpendicular to the plane of the loop in fig. The current induced in the loop is
a)
RvB
b)
zero
c)
vBL/R
d)
vBL
|
Sivappriya answered |
As the coil is neither moving inside the magnetic flux nor moving outside the magnetic flux the change is magnetic fulx is zero . therefore emf is zero hencecurrent induced in the coil is zero the thing is the coil moves in region of constant and uniform magnetic field ,so as said above current induced is zero option 2 is correct.
Which of the following is intermediate in Sandmeyer’s reaction?- a)Diazonium salt
- b)Hydronium ion
- c)Ammonium salt
- d)Nitronium ion
Correct answer is option 'A'. Can you explain this answer?
Which of the following is intermediate in Sandmeyer’s reaction?
a)
Diazonium salt
b)
Hydronium ion
c)
Ammonium salt
d)
Nitronium ion
|
Rajeev Saxena answered |
Diazonium salt is intermediate in Sandmeyer’s reaction.
Which of the following is major product of following reaction?
CH3CH = CH2 + HBr 
- a)2-Bromo propene
- b)1-Bromo propane
- c)1-Bromo propene
- d)2-Bromo propane
Correct answer is option 'D'. Can you explain this answer?
Which of the following is major product of following reaction?
CH3CH = CH2 + HBr
CH3CH = CH2 + HBr
a)
2-Bromo propene
b)
1-Bromo propane
c)
1-Bromo propene
d)
2-Bromo propane
|
Knowledge Hub answered |
The correct answer is Option D.
As HBr in the presence of a peroxide follows antimarkonikoff rule where the negative group should attach to the carbon having less no of hydrogen atoms.
As HBr in the presence of a peroxide follows antimarkonikoff rule where the negative group should attach to the carbon having less no of hydrogen atoms.
A long metal bar of 30 cm length is aligned along a north south line and moves eastward at a speed of 10 ms-1. A uniform magnetic field of 4.0 T points vertically downwards. If the south end of the bar has a potential of 0V, the induced potential at the north end of the bar is- a) + 12 V
- b)-12 V
- c)0 V
- d)Cannot be determined since there is not closed circuit
Correct answer is option 'A'. Can you explain this answer?
A long metal bar of 30 cm length is aligned along a north south line and moves eastward at a speed of 10 ms-1. A uniform magnetic field of 4.0 T points vertically downwards. If the south end of the bar has a potential of 0V, the induced potential at the north end of the bar is
a)
+ 12 V
b)
-12 V
c)
0 V
d)
Cannot be determined since there is not closed circuit
|
Anjali Sharma answered |
Induced emf =Blv=12V. It is induced in the northward direction by right hand rule (emf=
)
therefore if the south end of the pole has potential of 0V, the north end will have a potential of 12V.
)therefore if the south end of the pole has potential of 0V, the north end will have a potential of 12V.
A square coil ABCD is placed in x-y plane with its centre at origin. A long straight wire, passing through origin, carries a current in negative z-direction. Current in this wire increases with time.The induced current in the coil is
- a)clockwise
- b)anticlockwise
- c)zero
- d)alternating
Correct answer is option 'C'. Can you explain this answer?
A square coil ABCD is placed in x-y plane with its centre at origin. A long straight wire, passing through origin, carries a current in negative z-direction. Current in this wire increases with time.The induced current in the coil is
a)
clockwise
b)
anticlockwise
c)
zero
d)
alternating
|
Geetika Shah answered |
As magnetic field lines due to current carrying wire is along the surface and hence,
ϕ=B.A=BAcos90O=0
ϕ=B.A=BAcos90O=0
A conducting loop of radius R is present in a uniform magnetic field B perpendicular the plane of the ring. If radius R varies as a function of time `t', as R = R0 + t. The e.m.f induced in the loop is
a)2p (R0 + t) B clockwiseb)p(R0 + t)B clockwisec)2p(R0 + t)B anticlockwised)zeroCorrect answer is option 'C'. Can you explain this answer?
|
Lavanya Menon answered |
ε=− dϕ/dt
=−β(dA/dt)
=−β(dA/dt)
⇒∣ε∣=βπd(R0+t)2
=2πβ(R0+t)
Since inward flux is increasing the EMF will be induced counter clockwise.
=2πβ(R0+t)
Since inward flux is increasing the EMF will be induced counter clockwise.
Which of the following compound will not give addition reaction with bromine?- a)Propene
- b)1-Butene
- c)Iso butane
- d)Iso butene
Correct answer is option 'C'. Can you explain this answer?
Which of the following compound will not give addition reaction with bromine?
a)
Propene
b)
1-Butene
c)
Iso butane
d)
Iso butene
|
Om Desai answered |
The correct answer is Option C.
For Addition reaction π bond is required .Iso butane has no pi Bond .
Which of the following is formed in reaction mechanism of halogenation of alkanes in presence of UV light?- a)Carbocation
- b)Carbanion
- c)Diazonium ion
- d)Free radical
Correct answer is option 'D'. Can you explain this answer?
Which of the following is formed in reaction mechanism of halogenation of alkanes in presence of UV light?
a)
Carbocation
b)
Carbanion
c)
Diazonium ion
d)
Free radical
|
Niloni Soni answered |
In presence of uv light free radical mechanism takes place that is homolytic cleavage of covalent bond takes place. Carbocation and carbanion and diazonium ion forms when heterolytic cleavage of bond takes place.
. 
This reaction is known as:- a)Wurtz reaction
- b)Frankland reaction
- c)Fittig reaction
- d)Finkelstein reaction
Correct answer is option 'D'. Can you explain this answer?
.
This reaction is known as:
This reaction is known as:
a)
Wurtz reaction
b)
Frankland reaction
c)
Fittig reaction
d)
Finkelstein reaction
|
Hansa Sharma answered |
The correct answer is option D
where, X=Cl or Br.
This reaction is known as the Finkelstein reaction. Finkelstein's reaction is used to prepare alkyl iodides starting from alkyl chlorides and alkyl bromides.
where, X=Cl or Br.
This reaction is known as the Finkelstein reaction. Finkelstein's reaction is used to prepare alkyl iodides starting from alkyl chlorides and alkyl bromides.
Which of the following is the major product of following reaction?
CH3CH = CH2 + HBr in the presence of peroxide gives:- a)2 – bromopropane
- b)1 – bromopropene
- c)1 – bromopropane
- d)2 – bromopropene
Correct answer is option 'C'. Can you explain this answer?
Which of the following is the major product of following reaction?
CH3CH = CH2 + HBr in the presence of peroxide gives:
CH3CH = CH2 + HBr in the presence of peroxide gives:
a)
2 – bromopropane
b)
1 – bromopropene
c)
1 – bromopropane
d)
2 – bromopropene
|
|
Garima Kunwar answered |
In presence of HBr and peroxide anti markonikov's addition in supported. Hence 1-bromopropane will we major product
Two infinitely long conducting parallel rails are connected through a capacitor C as shown in the figure. A conductor of length l is moved with constant speed v0. Which of the following graph truly depicts the variation of current through the conductor with time ?
- a)
- b)
- c)
- d)
Correct answer is option 'C'. Can you explain this answer?
Two infinitely long conducting parallel rails are connected through a capacitor C as shown in the figure. A conductor of length l is moved with constant speed v0. Which of the following graph truly depicts the variation of current through the conductor with time ?
a)
b)
c)
d)
|
|
Anaya Patel answered |
By Faraday's Law of induction,
ε=− dϕ/dt
=−Bl (dx/dt) =−Blv0
This emf should induce the movement of charges creating a current. But due to the attached capacitor, all charges are conserved.
Thus I= dq/dt =0
The correct option is C.
ε=− dϕ/dt
=−Bl (dx/dt) =−Blv0
This emf should induce the movement of charges creating a current. But due to the attached capacitor, all charges are conserved.
Thus I= dq/dt =0
The correct option is C.
Two identical conductors P and Q are placed on two frictionless fixed conducting rails R and S in a uniform magnetic field directed into the plane. If P is moved in the direction shown in figure with a constant speed, then rod Q
- a)will be attracted towards P
- b)will be repelled away from P
- c)will remain stationary
- d)may be repelled or attracted towards P
Correct answer is option 'A'. Can you explain this answer?
Two identical conductors P and Q are placed on two frictionless fixed conducting rails R and S in a uniform magnetic field directed into the plane. If P is moved in the direction shown in figure with a constant speed, then rod Q
a)
will be attracted towards P
b)
will be repelled away from P
c)
will remain stationary
d)
may be repelled or attracted towards P
|
Neha Sharma answered |
As the conductor P moves away from Q, the area of the loop enclosed by the conductors and the rails increases. This in turn increases the flux through the loop.
EMF will be induced in such a way that the change in flux will be resisted. The induced current will cause Q to move towards P thereby reducing the area and thus the flux back.
EMF will be induced in such a way that the change in flux will be resisted. The induced current will cause Q to move towards P thereby reducing the area and thus the flux back.
A small conducting rod of length l, moves with a uniform velocity v in a uniform magnetic field B as shown in fig-
- a)Then the end X of the rod becomes positively charged
- b)the end Y of the rod becomes positively charged
- c)the entire rod is unevely charged
- d)the rod becomes hot due to joule heating
Correct answer is option 'B'. Can you explain this answer?
A small conducting rod of length l, moves with a uniform velocity v in a uniform magnetic field B as shown in fig-
a)
Then the end X of the rod becomes positively charged
b)
the end Y of the rod becomes positively charged
c)
the entire rod is unevely charged
d)
the rod becomes hot due to joule heating
|
Dr Manju Sen answered |
The rod is moving towards the right in a field directed into the page.
Now, if we apply Fleming's right hand rule, then the direction of induced current will be from end X to end Y.
But, according to Lenz's law the emf induced in the rod will be such that it opposes the motion of the rod.
Hence, the actual emf induced will be from end Y to end X. So, the current will also flow from end Y to end X.
Now, using the convention of current end Y should be positive and end X should be negative.
So, correct answer is option b
Now, if we apply Fleming's right hand rule, then the direction of induced current will be from end X to end Y.
But, according to Lenz's law the emf induced in the rod will be such that it opposes the motion of the rod.
Hence, the actual emf induced will be from end Y to end X. So, the current will also flow from end Y to end X.
Now, using the convention of current end Y should be positive and end X should be negative.
So, correct answer is option b
The instantaneous flux associated with a closed circuit of 10Ω resistance is indicated by the following reaction f = 6t2 _ 5t + 1, then the value in amperes of the induced current at t = 0.25 sec will be- a)1.2
- b)0.8
- c)6
- d)0.2
Correct answer is option 'D'. Can you explain this answer?
The instantaneous flux associated with a closed circuit of 10Ω resistance is indicated by the following reaction f = 6t2 _ 5t + 1, then the value in amperes of the induced current at t = 0.25 sec will be
a)
1.2
b)
0.8
c)
6
d)
0.2
|
Vivek Rana answered |
ϕ=6t2−5t+1
e= dϕ/dt =12t−5
at t=0.25sec
∣e∣=(12/4−5)=∣3−5∣=2
i=e/R=2/10=0.2A
e= dϕ/dt =12t−5
at t=0.25sec
∣e∣=(12/4−5)=∣3−5∣=2
i=e/R=2/10=0.2A
On reacting ethene with HCl we get:- a)Chloroethane
- b)Chloropropane
- c)Chloromethane
- d)None of these
Correct answer is option 'A'. Can you explain this answer?
On reacting ethene with HCl we get:
a)
Chloroethane
b)
Chloropropane
c)
Chloromethane
d)
None of these
|
Divey Sethi answered |
hydrogen chloride adds to ethene to make chloroethane:
CH2=CH2 + HCl → CH3CH2Cl
The number of turns in a long solenoid is 500. The area of cross-section of solenoid is 2 × 10-3 m2. If the value of magnetic induction, on passing a current of 2 amp, through it is 5 × 10-3 tesla, the magnitude of magnetic flux connected with it in webers will be- a)5 × 10-3
- b)10-2
- c)10-5
- d)2.5
Correct answer is option 'A'. Can you explain this answer?
The number of turns in a long solenoid is 500. The area of cross-section of solenoid is 2 × 10-3 m2. If the value of magnetic induction, on passing a current of 2 amp, through it is 5 × 10-3 tesla, the magnitude of magnetic flux connected with it in webers will be
a)
5 × 10-3
b)
10-2
c)
10-5
d)
2.5
|
Preeti Iyer answered |
Φ=BAN
=5x10-3x2x10-3x500
=5x10-3x1000x10-3
=5x10-3
=5x10-3x2x10-3x500
=5x10-3x1000x10-3
=5x10-3
What is the order of reactivity of following halogen acids on alcohols?
HI, HBr, HCl- a)HI < HBr < HCl
- b)HI > HBr > HCl
- c)HI > HCl > HBr
- d)HBr > HCl> HI
Correct answer is option 'B'. Can you explain this answer?
What is the order of reactivity of following halogen acids on alcohols?
HI, HBr, HCl
HI, HBr, HCl
a)
HI < HBr < HCl
b)
HI > HBr > HCl
c)
HI > HCl > HBr
d)
HBr > HCl> HI
|
|
Mira Sharma answered |
That atomic size increases from F to I, so bond length of H-X bond also gets increased and so bond dissociation energy decreases. Hence, ionisation of H-X increases, therefore acidic strength increases in the order
HF < HCl < HBr < HI
So, the reactivity of alcohols towards haloacids is in the order - HI>HBr>HCl
The dimensions of permeability of free space can be given by- a)[MLT-2A-2]
- b)[MLA-2]
- c)[ML-3T2A2]
- d)[MLA-1]
Correct answer is option 'A'. Can you explain this answer?
The dimensions of permeability of free space can be given by
a)
[MLT-2A-2]
b)
[MLA-2]
c)
[ML-3T2A2]
d)
[MLA-1]
|
|
Lavanya Menon answered |
In SI units, permeability is measured in Henries per meter H/m or Hm−1.
Henry has the dimensions of [ML2T−2A−2].
Dimensions for magnetic permeability will be [ML2T−2A−2]/[L]=[MLT−2A−2]
Henry has the dimensions of [ML2T−2A−2].
Dimensions for magnetic permeability will be [ML2T−2A−2]/[L]=[MLT−2A−2]
In an iron cored coil the iron core is removed so that the coil becomes an air cored coil. The inductance of the coil will- a)increase
- b)decrease
- c)remain the same
- d)initially increase and then decrease
Correct answer is option 'B'. Can you explain this answer?
In an iron cored coil the iron core is removed so that the coil becomes an air cored coil. The inductance of the coil will
a)
increase
b)
decrease
c)
remain the same
d)
initially increase and then decrease
|
|
Nandini Iyer answered |
In an iron cored coil the iron core is removed so that the coil becomes an air cored coil. The inductance of the coil will decrease.
Which of the following is formed by Swarts Reaction?- a)Alkyl iodide
- b)Alkyl fluoride
- c)Alkyl bromide
- d)Alkyl chloride
Correct answer is option 'B'. Can you explain this answer?
Which of the following is formed by Swarts Reaction?
a)
Alkyl iodide
b)
Alkyl fluoride
c)
Alkyl bromide
d)
Alkyl chloride
|
|
Rohit Shah answered |
In Swarts’ reaction, heavy metal fluorides are used as reagents. It is a reaction in which alkyl fluorides are formed when alkyl bromide or chloride reacts with metal fluorides. In the reaction, higher alkyl halide(R-Cl) react with lower metal halide (AgF) to form lower alkyl halide(R-F). If we don’t use heavy metal fluoride F ion cannot displace Cl/Br. The reaction will not occur or it may form some other compound.
Consider the situation shown in fig. The resistanceless wire AB is slid on the fixed rails with a constant velocity. If the wire AB is replaced by a resistanceless semicircular wire, the magnitude of the induced current will
- a)increase
- b)remain the same
- c)decrease
- d)increase or decrease depending on whether the semicircle bulges towards the resistance or away from it
Correct answer is option 'B'. Can you explain this answer?
Consider the situation shown in fig. The resistanceless wire AB is slid on the fixed rails with a constant velocity. If the wire AB is replaced by a resistanceless semicircular wire, the magnitude of the induced current will
a)
increase
b)
remain the same
c)
decrease
d)
increase or decrease depending on whether the semicircle bulges towards the resistance or away from it
|
Om Rana answered |
As we know I = B L V. But L would be a vector quantity here(If you have doubt why L would be vector quantity, see the derivation of induced current). So we have to take L effective. But L effective here will be diameter of the semicircle as it is perpendicular to both B and V vectors. As the diameter of the circle is same as the length of the wire we used first So there will be no change in the equation of induced current. So it remains same.
Which of the following evidences does not favour the Lamarckian concept of inheritance of acquired characters?- a)Lack of pigment in cave-dwelling animals
- b)Melanisation in peppered moth
- c)Absence of limbs in snakes
- d)Presence of webbed toes in aquatic birds
Correct answer is option 'B'. Can you explain this answer?
Which of the following evidences does not favour the Lamarckian concept of inheritance of acquired characters?
a)
Lack of pigment in cave-dwelling animals
b)
Melanisation in peppered moth
c)
Absence of limbs in snakes
d)
Presence of webbed toes in aquatic birds
|
|
Priya Menon answered |
According to Lamarckism (proposed by Lamarck), whatever characters an individual acquires in its life time due to internal vital force, effect of environment, new needs, use and disuse of organs, they are inherited to next generations. This process continues and after several generations, the variations are accumulated upto such an extent that they give rise to new species. Melanisation in peppered moth favours Darwin's theory of natural selection.
A thin wire of length 2m is perpendicular to the xy plane. It is moved with velocity 
through a region of magnetic induction 
Wb/m2. Then potential difference induced between the ends of the wire- a)2 volts
- b)4 volts
- c) 0 volts
- d)None of these
Correct answer is option 'A'. Can you explain this answer?
A thin wire of length 2m is perpendicular to the xy plane. It is moved with velocity through a region of magnetic induction Wb/m2. Then potential difference induced between the ends of the wire
through a region of magnetic induction Wb/m2. Then potential difference induced between the ends of the wirea)
2 volts
b)
4 volts
c)
0 volts
d)
None of these
|
|
Nikita Singh answered |
The magnetic flux through a stationary loop with resistance R varies during interval of time T as f = at (T _ t). The heat generated during this time neglecting the inductance of loop will be- a)
- b)
- c)
- d)
Correct answer is option 'A'. Can you explain this answer?
The magnetic flux through a stationary loop with resistance R varies during interval of time T as f = at (T _ t). The heat generated during this time neglecting the inductance of loop will be
a)
b)
c)
d)
|
|
Hansa Sharma answered |
E=dx/dt =d(a(Tt-t2))/dt=a(T-2t)
I=E/R=a(T-2t)/R
Heat liberated,
△k=I2Rdt
=(a2 /R)[T2t+(4t3/3)-2Tt2]T0
=△H=a2T3/3R
I=E/R=a(T-2t)/R
Heat liberated,
△k=I2Rdt
=(a2 /R)[T2t+(4t3/3)-2Tt2]T0
=△H=a2T3/3R
The north pole of a magnet is brought near a coil. The induced current in the coil as seen by an observer on the side of magnet will be- a)in the clockwise direction
- b)in the anticlockwise direction
- c)initially in the clockwise and then anticlockwise direction
- d)initially in the anticlockwise and then clockwise direction
Correct answer is option 'B'. Can you explain this answer?
The north pole of a magnet is brought near a coil. The induced current in the coil as seen by an observer on the side of magnet will be
a)
in the clockwise direction
b)
in the anticlockwise direction
c)
initially in the clockwise and then anticlockwise direction
d)
initially in the anticlockwise and then clockwise direction
|
|
Geetika Shah answered |
The direction of the current will be anticlockwise.
According to Lenz's law, the current in the coil will be induced in the direction that'll oppose the external magnetic field .
As the flux due to the external magnet is increasing ( as the N-pole is brought close ) , the coil will have to induce current in the anticlockwise direction to oppose this increase in flux and not in clockwise direction as that'll end up supporting the external flux.
According to Lenz's law, the current in the coil will be induced in the direction that'll oppose the external magnetic field .
As the flux due to the external magnet is increasing ( as the N-pole is brought close ) , the coil will have to induce current in the anticlockwise direction to oppose this increase in flux and not in clockwise direction as that'll end up supporting the external flux.
Read the following statements carefully and select the correct ones
(i) Alfred Wallace, a naturalist who worked in Malay Archipelago had also come to similar conclusions as Darwin around the same time
(ii) August Weismann by careful experimentation demonstrated that life comes only from pre-existing life.
(iii) The organs which have the same fundamental structure but are different in functions are called homologous organs
(iv) Rate of appearance' of new. form is inversely proportional to life span of organism- a)(i) and (iii)
- b)(i) and (ii)
- c)(ii) and (iv)
- d)(iii) and (iv)
Correct answer is option 'A'. Can you explain this answer?
Read the following statements carefully and select the correct ones
(i) Alfred Wallace, a naturalist who worked in Malay Archipelago had also come to similar conclusions as Darwin around the same time
(ii) August Weismann by careful experimentation demonstrated that life comes only from pre-existing life.
(iii) The organs which have the same fundamental structure but are different in functions are called homologous organs
(iv) Rate of appearance' of new. form is inversely proportional to life span of organism
(i) Alfred Wallace, a naturalist who worked in Malay Archipelago had also come to similar conclusions as Darwin around the same time
(ii) August Weismann by careful experimentation demonstrated that life comes only from pre-existing life.
(iii) The organs which have the same fundamental structure but are different in functions are called homologous organs
(iv) Rate of appearance' of new. form is inversely proportional to life span of organism
a)
(i) and (iii)
b)
(i) and (ii)
c)
(ii) and (iv)
d)
(iii) and (iv)
|
|
Meera Singh answered |
Louis Pasteur by careful experimentation demonstrated that life comes only from pre-existing life. Rate of appearance of new forms is directly proportional to life span of organism. Microbes that divide fast evolve fast. For same process to occur in fish or fowl will take million of years.
Which one of the following phenomena supports Darwin's concept of natural selection in organic evolution?- a)Development of transgenic animals
- b)Production of 'Dolly', the sheep by cloning
- c)Prevalence of pesticide resistant insects
- d)Development of organs from 'stem cells' for organ transplantation
Correct answer is option 'C'. Can you explain this answer?
Which one of the following phenomena supports Darwin's concept of natural selection in organic evolution?
a)
Development of transgenic animals
b)
Production of 'Dolly', the sheep by cloning
c)
Prevalence of pesticide resistant insects
d)
Development of organs from 'stem cells' for organ transplantation
|
|
Vivek Patel answered |
Prevalence of pesticide resistant insects supports natural selection theory, e.g., DDT was thought to be an effective insecticide against household pests (like mosquitoes, houseflies, body lice, etc.) in 1945. But, within 2 to 3 years of its introduction, new DDT resistant mosquitoes appeared in the population. These mutant strains, soon became well established in the population by natural selection and thus replaced the original DDT - sensitive mosquitoes.
Darwinism explains all the following except- a)off spring with better traits that over come competition are best suited for the environment
- b)variations may or may not be inherited from parents to offspring through genes
- c)within each species, there are variations
- d)organisms tend to produce more number of offspring than can survive
Correct answer is option 'B'. Can you explain this answer?
Darwinism explains all the following except
a)
off spring with better traits that over come competition are best suited for the environment
b)
variations may or may not be inherited from parents to offspring through genes
c)
within each species, there are variations
d)
organisms tend to produce more number of offspring than can survive
|
|
Preeti Iyer answered |
The main drawback of Darwinism is lack of knowledge of heredity. Darwin's theory could not explain the inheritance of variations from parents to off springs through genes.
Two identical coaxial circular loops carry a current i each circulating in the same direction. If the loops approach each other- a)the current in each will decrease
- b)the current in each will increase
- c)the current in each will remain the same
- d)the current in one will increase and in other will decrease
Correct answer is option 'A'. Can you explain this answer?
Two identical coaxial circular loops carry a current i each circulating in the same direction. If the loops approach each other
a)
the current in each will decrease
b)
the current in each will increase
c)
the current in each will remain the same
d)
the current in one will increase and in other will decrease
|
Tejas Desai answered |
Ans.
Option (a)
As coils approach each other, the flux linked with each coil increases. A current will be induced in each coil which will try to decrease the flux. This implies induced current in each coil will be opposite to initial current. So, current in each coil decreases as the coils approach each other.
When a magnet is being moved towards a coil, the induced emf does not depend upon- a)the number of turns of the coil
- b)the motion of the magnet
- c)the magnetic moment of the magnet
- d)the resistance of the coil
Correct answer is option 'D'. Can you explain this answer?
When a magnet is being moved towards a coil, the induced emf does not depend upon
a)
the number of turns of the coil
b)
the motion of the magnet
c)
the magnetic moment of the magnet
d)
the resistance of the coil
|
|
Chirag Joshi answered |
The magnitude of induced emf is independent of the resistance of the coil.
∴e=−dϕ/dt=−N (d/dt) [(BA)/dt]
Thus, e depends upon N, B and A.
But induced current depends upon R.
∴e=−dϕ/dt=−N (d/dt) [(BA)/dt]
Thus, e depends upon N, B and A.
But induced current depends upon R.
Which of the following are the two key concepts of Darwinian theory of evolution?- a)Genetic drift and mutation
- b)Adaptive radiation and homology
- c)Mutation and natural selection
- d)Branching descent and natural selection
Correct answer is option 'D'. Can you explain this answer?
Which of the following are the two key concepts of Darwinian theory of evolution?
a)
Genetic drift and mutation
b)
Adaptive radiation and homology
c)
Mutation and natural selection
d)
Branching descent and natural selection
|
|
Anjali Sharma answered |
According to Darwin's theory of evolution, nature selects the fittest. Fitness is based on characteristics which are inherited. Therefore, there must be a genetic basis for getting selected and to evolve. Some organisms are better adapted to survive in an otherwise hostile environment. Adaptative ability is inherited. Fitness is the end result of the ability to adapt and get selected by nature. Therefore, branching descent (inheritance) and natural selection are the two key concepts of Darwin's theory of evolution.
A closed planar wire loop of area A and arbitrary shape is placed in a uniform magnetic field of magnitude B, with its plane perpendicular to magnetic field. The resistance of the wire loop is R. The loop is now turned upside down by 180° so that its plane again becomes perpendicular to the magnetic field. The total charge that must have flowen through the wire ring in the process is- a)< AB/R
- b)= AB/R
- c)= 2AB/R
- d)None
Correct answer is option 'C'. Can you explain this answer?
A closed planar wire loop of area A and arbitrary shape is placed in a uniform magnetic field of magnitude B, with its plane perpendicular to magnetic field. The resistance of the wire loop is R. The loop is now turned upside down by 180° so that its plane again becomes perpendicular to the magnetic field. The total charge that must have flowen through the wire ring in the process is
a)
< AB/R
b)
= AB/R
c)
= 2AB/R
d)
None
|
Rajesh Chatterjee answered |
Induced emf= d(flux)/dt=R[dq/dt]
⇒Δq= Δ(flux)/R=2BA/R
⇒Δq= Δ(flux)/R=2BA/R
A metal sheet is placed in a variable magnetic field which is increasing from zero to maximum. Induced current flows in the directions as shown in figure. The direction of magnetic field will be -
- a)normal to the paper, inwards
- b)normal to the paper, outwards.
- c)from east to west
- d)from north to south
Correct answer is option 'B'. Can you explain this answer?
A metal sheet is placed in a variable magnetic field which is increasing from zero to maximum. Induced current flows in the directions as shown in figure. The direction of magnetic field will be -
a)
normal to the paper, inwards
b)
normal to the paper, outwards.
c)
from east to west
d)
from north to south
|
|
Nandini Iyer answered |
The direction of these circular magnetic lines is dependent upon the direction of current. The density of the induced magnetic field is directly proportional to the magnitude of the current. Direction of the circular magnetic field lines can be given by Maxwell's right hand grip rule or Right handed cork screw rule.
Which one of the following sequences was proposed by Darwin and Wallace for organic evolution?- a)Overproduction, variations, constancy of population size, natural selection
- b)Variations, constancy of population size, over production, natural selection
- c)Overproduction, constancy of population size, variations, natural selection
- d)Variations, natural selection, overproduction, constancy of population size
Correct answer is option 'C'. Can you explain this answer?
Which one of the following sequences was proposed by Darwin and Wallace for organic evolution?
a)
Overproduction, variations, constancy of population size, natural selection
b)
Variations, constancy of population size, over production, natural selection
c)
Overproduction, constancy of population size, variations, natural selection
d)
Variations, natural selection, overproduction, constancy of population size
|
|
Meera Singh answered |
Though living organisms tend to multiply geometrically, the number of individuals of a species tend to remain constant over a long period of time. Out of heterogeneous population (due to the variation) best adapted individuals are selected by nature.
Single step large mutation leading to speciation is also called- a)founder effect
- b)saltation
- c)branching descent
- d)natural selection
Correct answer is option 'B'. Can you explain this answer?
Single step large mutation leading to speciation is also called
a)
founder effect
b)
saltation
c)
branching descent
d)
natural selection
|
Dev Patel answered |
Hugo de Vries believed that mutation causes evolution and not the minor heritable variations which were mentioned by Darwin. According to Darwin, evolution was gradual while de Vries believed mutations appear suddenly and hence called it saltation (single step large mutation)
A field of 5 x 104/p ampere-turns/metre acts at right angles to a coil of 50 turns of area 10-2 m2. The coil is removed from the field in 0.1 second. Then the induced emf in the coil is- a)0.1 V
- b)80 KV
- c)7.96 V
- d)none of the above
Correct answer is option 'A'. Can you explain this answer?
A field of 5 x 104/p ampere-turns/metre acts at right angles to a coil of 50 turns of area 10-2 m2. The coil is removed from the field in 0.1 second. Then the induced emf in the coil is
a)
0.1 V
b)
80 KV
c)
7.96 V
d)
none of the above
|
|
Siddharth Tiwari answered |
Given data:
Field strength, H = 5 x 10^4/p A-turns/m
Number of turns, N = 50
Area, A = 10^-2 m^2
Time, t = 0.1 s
Formula used:
The induced emf in a coil is given by the formula,
E = -NdΦ/dt
where N is the number of turns in the coil, Φ is the magnetic flux passing through the coil, and dt is the time for which the magnetic flux changes.
Calculation:
Magnetic flux density, B = μH
where μ is the permeability of the medium, which is taken as μ = μ0 for air, and μ0 = 4π x 10^-7 T-m/A
B = μH = 4π x 10^-7 x 5 x 10^4/p = 2π/p x 10^-2 T
Magnetic flux passing through the coil, Φ = NBA
where B is the magnetic flux density, A is the area of the coil
Φ = NBA = 2π/p x 10^-2 x 50 = π/p x 10^-1 Wb
The rate of change of magnetic flux, dΦ/dt = Φ/t = π/p x 10^-1/0.1 = π/p x V/s
The induced emf in the coil, E = -NdΦ/dt
E = -50 x π/p x 10^-1/0.1 = -5π/p V
Since the emf is induced in the opposite direction to the change in magnetic flux, we take the magnitude of the emf.
E = 5π/p V = 1.6 V/p V (approx.)
Therefore, the induced emf in the coil is 0.1 V (approx.), which is closest to option (a).
Field strength, H = 5 x 10^4/p A-turns/m
Number of turns, N = 50
Area, A = 10^-2 m^2
Time, t = 0.1 s
Formula used:
The induced emf in a coil is given by the formula,
E = -NdΦ/dt
where N is the number of turns in the coil, Φ is the magnetic flux passing through the coil, and dt is the time for which the magnetic flux changes.
Calculation:
Magnetic flux density, B = μH
where μ is the permeability of the medium, which is taken as μ = μ0 for air, and μ0 = 4π x 10^-7 T-m/A
B = μH = 4π x 10^-7 x 5 x 10^4/p = 2π/p x 10^-2 T
Magnetic flux passing through the coil, Φ = NBA
where B is the magnetic flux density, A is the area of the coil
Φ = NBA = 2π/p x 10^-2 x 50 = π/p x 10^-1 Wb
The rate of change of magnetic flux, dΦ/dt = Φ/t = π/p x 10^-1/0.1 = π/p x V/s
The induced emf in the coil, E = -NdΦ/dt
E = -50 x π/p x 10^-1/0.1 = -5π/p V
Since the emf is induced in the opposite direction to the change in magnetic flux, we take the magnitude of the emf.
E = 5π/p V = 1.6 V/p V (approx.)
Therefore, the induced emf in the coil is 0.1 V (approx.), which is closest to option (a).
A long solenoid contains 1000 turns/cm and an alternating current of peak value 1A is flowing in it. A search coil of area of cross-section 1 × 10-4 m2 and having 50 turns is placed inside the solenoid with its plane perpendicular to the axis of the solenoid. A peak voltage of 2p2 × 10-2V is produced in the search coil. The frequency of current in the solenoid will be- a)50 Hz
- b)100 Hz
- c)500 Hz
- d)1000 Hz
Correct answer is option 'A'. Can you explain this answer?
A long solenoid contains 1000 turns/cm and an alternating current of peak value 1A is flowing in it. A search coil of area of cross-section 1 × 10-4 m2 and having 50 turns is placed inside the solenoid with its plane perpendicular to the axis of the solenoid. A peak voltage of 2p2 × 10-2V is produced in the search coil. The frequency of current in the solenoid will be
a)
50 Hz
b)
100 Hz
c)
500 Hz
d)
1000 Hz
|
|
Navpreet Singh answered |
Each of us is part of the ongoing evolution of the species. Which of the following occurrences would have the greatest impact on the future biological evolution of the human population?- a)A mutation occurs in one of your sperm or egg cells
- b)You do exercise every day so that you stay physically fit and healthy
- c)You move to Kerala, the state of highest medical facilities and literacy
- d)You encourage your children to develop their intellectual abilities
Correct answer is option 'A'. Can you explain this answer?
Each of us is part of the ongoing evolution of the species. Which of the following occurrences would have the greatest impact on the future biological evolution of the human population?
a)
A mutation occurs in one of your sperm or egg cells
b)
You do exercise every day so that you stay physically fit and healthy
c)
You move to Kerala, the state of highest medical facilities and literacy
d)
You encourage your children to develop their intellectual abilities
|
|
Ajay Yadav answered |
A mutation in sperms or egg cells means mutation in offspring. This will have greatest impact on the future biological evolution of the human population.
What was the primary goal of S.L. Miller's experiment conducted in 1953?- a) To understand volcanic activity
- b) To create life in a laboratory
- c) To study meteorite composition
- d) To investigate chemical evolution
Correct answer is option 'D'. Can you explain this answer?
What was the primary goal of S.L. Miller's experiment conducted in 1953?
a)
To understand volcanic activity
b)
To create life in a laboratory
c)
To study meteorite composition
d)
To investigate chemical evolution
|
EduRev NEET answered |
S.L. Miller's experiment aimed to explore the origins of organic compounds and their role in chemical evolution.
The diversity in the type of beaks of finches adapted to different feeding habits on the Galapagos Islands, as observed by Darwin, provides evidence for- a)intraspecific competition
- b)interspecific competition
- c)origin of species by natural selection
- d)origin of species by mutation
Correct answer is option 'C'. Can you explain this answer?
The diversity in the type of beaks of finches adapted to different feeding habits on the Galapagos Islands, as observed by Darwin, provides evidence for
a)
intraspecific competition
b)
interspecific competition
c)
origin of species by natural selection
d)
origin of species by mutation
|
|
Anjali Sharma answered |
Darwin during his famous voyage, observed that finches from various islands of Galapagos had beaks of different sizes and shapes. He observed that this was due to adaptation to different available food types. He concluded that the ancestral finches on reaching different islands occupied all empty ecological niches in absence of competition and evolved into different species. This provides evidences for origin of species by natural selection.
Consider the following three statements and select the correct option stating which one is true (T) and which one is false (F)
(i) Oparin of Russia and Haldane of England proposed that the first form of life could have come from pre-existing non-living organic molecules (e.g., RNA, protein, etc.) and that formation of life was preceded by chemical evolution
(ii) Based on observations made during a sea voyage around the world, Charles Darwin concluded that existing living forms share similarities to varying degrees only among themselves
(iii) Evolution by natural selection must have started when cellular forms of life with different metabolic capability originated on Earth
- a)a
- b)b
- c)c
- d)d
Correct answer is option 'B'. Can you explain this answer?
Consider the following three statements and select the correct option stating which one is true (T) and which one is false (F)
(i) Oparin of Russia and Haldane of England proposed that the first form of life could have come from pre-existing non-living organic molecules (e.g., RNA, protein, etc.) and that formation of life was preceded by chemical evolution
(ii) Based on observations made during a sea voyage around the world, Charles Darwin concluded that existing living forms share similarities to varying degrees only among themselves
(iii) Evolution by natural selection must have started when cellular forms of life with different metabolic capability originated on Earth
(i) Oparin of Russia and Haldane of England proposed that the first form of life could have come from pre-existing non-living organic molecules (e.g., RNA, protein, etc.) and that formation of life was preceded by chemical evolution
(ii) Based on observations made during a sea voyage around the world, Charles Darwin concluded that existing living forms share similarities to varying degrees only among themselves
(iii) Evolution by natural selection must have started when cellular forms of life with different metabolic capability originated on Earth
a)
a
b)
b
c)
c
d)
d
|
|
Meera Singh answered |
Based on observations made during a sea voyage around the world, Charles Darwin concluded that existing living forms share similarities to varying degrees not only among themselves but also with life forms that existed millions of years ago.
What did Oparin and Haldane propose about the origin of the first forms of life?- a) They came from pre-existing non-living organic molecules.
- b) They originated from extraterrestrial sources.
- c) They evolved directly from inorganic materials.
- d) They were created through divine intervention.
Correct answer is option 'A'. Can you explain this answer?
What did Oparin and Haldane propose about the origin of the first forms of life?
a)
They came from pre-existing non-living organic molecules.
b)
They originated from extraterrestrial sources.
c)
They evolved directly from inorganic materials.
d)
They were created through divine intervention.
|
Stepway Academy answered |
Oparin and Haldane proposed that the first forms of life originated from pre-existing non-living organic molecules that formed under the conditions present on early Earth.
square wire loop of 10.0 cm side lies at right angles to a uniform magnetic field of 20T. A 10 V light bulb is in a series with the loop as shown in the fig. The magnetic field is decreasing steadily to zero over a time interval Dt. The bulb will shine with full brightness if Dt is equal to
- a)20 ms
- b)0.02 ms
- c)2 ms
- d)0.2 ms
Correct answer is option 'A'. Can you explain this answer?
square wire loop of 10.0 cm side lies at right angles to a uniform magnetic field of 20T. A 10 V light bulb is in a series with the loop as shown in the fig. The magnetic field is decreasing steadily to zero over a time interval Dt. The bulb will shine with full brightness if Dt is equal to
a)
20 ms
b)
0.02 ms
c)
2 ms
d)
0.2 ms
|
Anjali Reddy answered |
An electron is moving in a circular orbit of radius R with an angular acceleration a. At the centre of the orbit is kept a conducting loop of radius r, (r < < R). The e.m.f induced in the smaller loop due to the motion of the electron is- a)zero, since charge on electron in constant
- b)
- c)
- d)none of these
Correct answer is option 'B'. Can you explain this answer?
An electron is moving in a circular orbit of radius R with an angular acceleration a. At the centre of the orbit is kept a conducting loop of radius r, (r < < R). The e.m.f induced in the smaller loop due to the motion of the electron is
a)
zero, since charge on electron in constant
b)
c)
d)
none of these
|
|
Ram Mohith answered |
Note that since "r" is much smaller than "R" we can treat the loop to be as a point with respect to the outer orbit.
By the statement "Survival of the Fittest" Darwin meant that...............- a)The strongest of all species survives
- b)The most intelligent of the species survives
- c)The cleverest of the species survives
- d)The most adaptable of the species to changes survives
Correct answer is option 'D'. Can you explain this answer?
By the statement "Survival of the Fittest" Darwin meant that...............
a)
The strongest of all species survives
b)
The most intelligent of the species survives
c)
The cleverest of the species survives
d)
The most adaptable of the species to changes survives
|
|
Priya Menon answered |
The organisms which are provided with favourable variations would survive, because they are the fittest to face their surroundings, while the unfit are eliminated. Originally it was an idea of Herbert Spencer (1820-1903) who used the phrase 'the survival of the fittest' first time. While Darwin named it as natural selection.
According to Lamarckism, long necked giraffes evolved because- a)nature selected only long necked ones
- b)humans preferred only long necked ones
- c)short necks suddenly changed into long necks
- d)of stretching of necks over many generations by short necked ones
Correct answer is option 'D'. Can you explain this answer?
According to Lamarckism, long necked giraffes evolved because
a)
nature selected only long necked ones
b)
humans preferred only long necked ones
c)
short necks suddenly changed into long necks
d)
of stretching of necks over many generations by short necked ones
|
Jyoti Sengupta answered |
According to Lamarckism, the ancestors of giraffe had small neck and forelimbs and were like horses. They were residing in places with no surface vegetation, therefore, they had to stretch their neck and forelimbs to take the leaves for food. This led to slight elongation of these parts. Whatever they acquired in one generation was transmitted to the next generation with the result that a race of long necked and long forelimbed giraffes were developed.
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