datavorous/entrance-exam-dataset huggingface dataset:
A spring of force constant k is cut into two pieces such that one piece is double the length of the other. Then the long piece will have a force constant of

Options:
A 2k3

B 3k2
C 3 k

D 6 k

The correct answer is:
3k2

Solution:
l1=2l2
Therefore
lâ¡ 1 = 2 3 lâ¡

Force constant k
â = 1 length of spring
k1=32k

Topic: Physics, Oscillations, NEET
A spring of spring constant 5Ã103 N m-1 is stretched initially by 5 cm from the unstretched position. Then the work required to stretch it further by another 5 cm is

Options:
A 12.50 N m

B 18.75 N m

C 25 N m

D 6.25 N m

The correct answer is:
18.75 N m

Solution:
W1=12kx12=1Ã52Ã103Ã5Ã10-22=6.25 J
W2=12kx1+x22
=12Ã5Ã1035Ã10-2+5Ã10-22=25 J
Net work done =W2-W1
=25-6.25=18.75 J=18.75 N m

Topic: Physics, Work Power Energy, NEET
A spring of spring constant 200 N m-1 has a block of mass 1 kg hanging at its one end and from another end, spring is attached to a ceiling of an elevator. The elevator rising upwards with an acceleration of g3. When acceleration suddenly ceases, then angular velocity and elongation during the time when the elevator is accelerating

Options:
A 14.14 rad s-1, 0.07 m

B 13 rad s-1, 0.1 m
C 14 rad s-1, 0.05 m
D 10 rad s-1, 0.07 m

The correct answer is:
14.14 rad s-1, 0.07 m

Solution:
The angular frequency under all circumstances is
Ï = k m
= 2 0 0 1 = 1 4 . 1 4 rad / s
When elevator is moving up, using NLM
T - mg = mg 3 â T = 4 mg 3
This tension elongates the spring by x
T = kx â x = 4 mg 3 k = 0 . 0 7 m

Topic: Physics, Oscillations, NEET
A spring which is initially in its natural length, first stretched by a length x and then again by a further length x. The work done in the first case is W and in the second case W1. Then,

Options:
A W1=4Â W
B W1=3 W
C W1=W
D W1=2Â W

The correct answer is:
W1=3 W

Solution:
Since, we know, work done in stretching a spring from x1 to x2 is
W=12kx22-x12
In 1st case, W=12kx2-0=12kx2 .... (i)
In 2nd case, W1=12k2x2-x2=12k4x2-x2
=12k.3x2=3.12kx2
=3W [From Eq. (i)]

Topic: Physics, Work Power Energy, NEET
A square coil ACDE with its plane vertical is released from rest in a horizontal uniform magnetic field B â of length 2L. The acceleration of the coil is

Options:
A less than g for all the time till the loop crosses the magnetic field completely.
B less than g when it enters the field and greater than g when it comes out of the field.
C g all the time.
D less than g when enters and comes out of the field but equal to g when it is within the field.

The correct answer is:
less than g when enters and comes out of the field but equal to g when it is within the field.

Solution:
When the coil is within the field, there is no change in magnetic flux passing through it. Thus, no current will be induced and the acceleration will be g. But according to Lenz's law, the induced current will oppose its motion when it enters or leaves the field. Therefore, acceleration will be less than g.

Topic: Physics, Electromagnetic Induction, NEET
A square coil of side 25 cm having 1000 turns is rotated with a uniform speed in a magnetic field about an axis perpendicular to the direction of the field. At an instant t, the EMF induced in the coil is E =200sin100Ït. The magnetic induction is

Options:
A 0.02 T
B 10-3Â T
C 0.1 T
D 0.01 T

The correct answer is:
0.01 T

Solution:
e=200sinâ¡100 Ït
We have,
e0=200
Ï=100 Ï
â´BANÏ=e0
â´B=e0ANÏ
B=200(0.25Ã0.25)Ã1000Ã100Ï
B=0.01 T

Topic: Physics, Electromagnetic Induction, NEET
A square conducting loop of side length L carries a current I. The magnetic field at the centre of the loop is

Options:
A independent of L
B proportional to L2
C inversely proportional to L
D linearly proportional to L

The correct answer is:
inversely proportional to L

Solution:
Field due to wire AB at the center,
BAB=Î¼0I4ÏL2sinâ¡45Â°+sinâ¡45Â°
Bcenter=4BAB
Bcenter=4Î¼0I4ÏL212+12
Bcenter=22Î¼0IÏL
Bcenterâ1L

Topic: Physics, Magnetic Effects of Current, NEET
A square frame of side 10 cm and a long straight wire carrying current 1 A are in the plane of the paper. Starting from close to the wire, the frame moves towards the right with a constant speed of 10 msâ1 (see figure). The e.m.f induced at the time the left arm of the frame is at x=10 cm from the wire is

Options:
A 0 . 7 5 μ V
B 1 Î¼ V
C 2 μ V
D 0 . 5 μ V

The correct answer is:
1 Î¼ V

Solution:
d Ï = Î¼ 0 i 2 Ï y a dy
Ï = Î¼ 0 i a 2 Ï â« x x + a dy y = Î¼ 0 i a 2 Ï ln x + a - ln x
E.m.f = - dÏ dt = - Î¼ 0 i a 2 Ï 1 x + a dx dt - 1 x dx dt
=Î¼0ia2Ïa.vxx+a=Î¼02Ï.ia2vxx+a=2Ã10-7Ã1Ã0.12Ã100.1Ã0.2=1Î¼V
Alternative method:
Consider two sides which are perpendicular to the velocity as case of motional e.m.f.
E=E1-E2=B1âB2Vl
=Î¼0I2Ï1r1-1r2V1
=2Ã10-7Ã1(10.1-10.2)10Ã0.1
=10-6v=1 Î¼V

Topic: Physics, Electromagnetic Induction, NEET
A square loop ABCD , carrying a current i , is placed near and coplanar with a long straight conductor XY carrying current I
Then,

Options:
A there is no net force on the loop
B the loop will be attracted by the conductor only if the current in the loop flows clockwise
C the loop will be attracted by the conductor only if the current in the loop flows anticlockwise
D the loop will always be attracted by the conductor

The correct answer is:
the loop will be attracted by the conductor only if the current in the loop flows clockwise

Solution:
Force on part BC and AD will be equal and opposite whether current is clockwise or anticlockwise.
Intensity of field is more at AB than at CD , therefore magnitude of force on AB will be more than CD . Therefore the loop will be attracted by the conductor if the current in the loop flows clockwise.

Topic: Physics, Magnetic Effects of Current, NEET
A square loop ABCD carrying a current i , is placed near and coplanar with a long straight conductor XY carrying a current I , the net force on the loop will be:

Options:
A 2μ0Ii3π
B μ0Ii2π
C 2μ0IiL3π
D μ0IiL2π

The correct answer is:
2μ0Ii3π

Solution:
F1=μ0IiL2πL2 =μ0Iiπ
F 2 =μ0IiL2π3L2=μ0Ii3π
∴Fnet=F1-F2
Fnet=23μ0Iiπ

Topic: Physics, Magnetic Effects of Current, NEET, NEET 2016 (Phase 1)
A square loop, carrying a steady current I, is placed in a horizontal plane near a long straight conductor carrying a steady current I1 at a distance d from the conductor as shown in figure. The loop will experience

Options:
A A net repulsive force away from the conductor
B A net torque acting upward perpendicular to the horizontal plane
C A net torque acting downward normal to the horizontal plane
D A net attractive force toward the conductor

The correct answer is:
A net attractive force toward the conductor

Solution:
F 1 > F 2 as F∝ 1 d , and F 3 and F 4 are equal and opposite. Hence, the net attraction force will be towards the conductor.

Topic: Physics, Magnetic Effects of Current, NEET
A square loop of side 1 m and resistance 1 Ω is placed in a magnetic field of 0.5 T. If the plane of loop is perpendicular to the direction of magnetic field, the magnetic flux through the loop is:

Options:
A 0.5 weber
B 1 weber
C zero weber
D 2 weber

The correct answer is:
0.5 weber

Solution:
As plane of loop is perpendicular to the direction of magnetic field, therefore direction of area vector will be parallel to magnetic field.

Magnetic flux is given by,

ϕ=B→·A→=0.512cos0°=0.5 Wb

Topic: Physics, Electromagnetic Induction, NEET, NEET 2022 (Phase 1)
A square loop of side a is placed at a distance a length away from a long wire carrying a current I1 . If the loop carries a current I2 as shown in the figure. Then the nature of the force and its amount is

Options:
A μ0I1I22πa , attractive
B μ0I1I24π , attractive
C μ0I1I24π , repulsive
D μ0I1I24πa , repulsive

The correct answer is:
μ0I1I24π , attractive

Solution:
From the figure it is clear that F2 & F4 cancel each other, but F1>F3
Fnet=F1-F3
Fnet=μ0I1I22πaa-μ0I1I24πaa
Fnet=μ0I1I24π

Topic: Physics, Magnetic Effects of Current, NEET
A square loop of side a is rotating about its diagonal with angular velocity Ï in a perpendicular magnetic field Bâ . It has 10 turns. The emf induced is

Options:
A Ba2sin⁡ωt
B Ba2cos⁡ωt
C 52Ba2
D 10Ba2ωsin⁡ωt

The correct answer is:
10Ba2ωsin⁡ωt

Solution:
Magnetic flux linked with loop at any instant,
ϕ=BAcos⁡θ
ϕ=Ba2cos⁡ωt
Emf induced
∴ε=-Ndϕdt=NBa2ωsin⁡ωt
ε=10Ba2ωsin⁡ωt

Topic: Physics, Electromagnetic Induction, NEET
A square metal loop of side 10 cm and resistance 1 Î© is moved with a constant velocity partly inside a uniform magnetic field of 2 Wb m-2, directed into the paper, as shown in the figure. The loop is connected to a network of five resistors each of value 3 Î©. If a steady current of 1 mA flows in the loop, then the speed of the loop is -

Options:
A 0.5  cm s −1
B 1  cm s −1
C 2â cm s â1
D 4  cm s −1

The correct answer is:
2â cm s â1

Solution:
The network appears as a Balanced Wheatstone bridge. Therefore, no current will flow through the bridge resistance. Thus, the resistance will have no effect on the network. Set of two series resistors each values 3âÎ© is now parallel to each other. Therefore the equivalent resistance of the balanced network is,

â´ R= 1 ( 1 3+3 + 1 3+3 ) = 1 ( 1 6 + 1 6 ) = 1 ( 2 6 ) = 6 2 =3âÎ©
The balanced network is in series with the 1âÎ©âinternal resistance. Therefore, the equivalant resistance of the network is,
R'=3â+1=4âÎ©
The direction of motion of free electron in rod in magnetic field is towards right and it has a velocity v. Theâinducedâemfâis,
e=vBl=IR'
Therefore, the velocity is,

v= IR' Bl
v= ( 1Ã 10 â3 )( 4 ) ( 2 )( 10Ã 10 â2 ) =2Ã 10 â2 â m s â1
v=2â cm s â1

Topic: Physics, Electromagnetic Induction, NEET
A square of a side a is cut from a square of side 2a as shown in the figure. Mass of this square with a hole is M. Then its moment of inertia about an axis passing through its centre of mass and perpendicular to its plane will be

Options:
A Ma26
B 2Ma26
C 4Ma26
D 5Ma26

The correct answer is:
5Ma26

Solution:
Given plate has mass M and area 3a2
A square plate of side 2a (made of the same material) has mass 4M3 and
Therefore moment of inertia about its axis is
I1=164M32a2
A square plate of side a (made of the same material) has mass M3 and
Therefore moment of inertia about its axis is I2=16M3a2
Moment of inertia of the given plate is
I=I1-I2=56Ma2

Topic: Physics, Rotational Motion, NEET
A square plate is kept in YZ plane. Then according to perpendicular axis theorem

Options:
A Iz=Ix+Iy
B Ix=Iy+Iz
C Iy=Ix+Iz
D all of the above

The correct answer is:
Ix=Iy+Iz

Solution:
For a mass distribution in YZ- plane
Ix=Iy+Iz

Topic: Physics, Rotational Motion, NEET
A square plate of edge d and a circular disc of diameter d are placed touching each other at the midpoint of an edge of the plate as shown. Then the centre of mass of the combination will be (assume same mass per unit area for the two plates)

Options:
A 2d2+π left to the centre of the disc
B 2d2+π right to the centre of the disc
C 4d4+π right to the centre of the disc
D 4d4+π left to the center of the disc

The correct answer is:
4d4+π right to the centre of the disc

Solution:
Taking centre of the disc as origin,
x coordinate of the disc,

x1=0
x coordinate of Plate,
x2=d2+d2=d

centre of mass of the combination,
xcm=A1x1+A2x2A1+A2
xcm=0+d2dπd24+d2
xcm=4d4+π

Topic: Physics, Center of Mass Momentum and Collision, NEET
A square surface of side $L$ metre in the plane of the paper is placed in a uniform electric field $E$ (volt/m) acting along the same place at an angle $\theta$ with the horizontal side of the square as shown in figure. The electric flux linked to the surface in unit of $V-m$, is

Options:
A $\mathrm{EL}^2$
B $\mathrm{EL}^2 \cos \theta$
C $\mathrm{EL}^2 \sin \theta$
D 0

The correct answer is:
0

Solution:
Flux of electric field $\vec{E}$ through any area $A$ is defined as $\phi=\mathrm{E} \cdot \mathrm{A} \cos \theta$ or $\phi=\overrightarrow{\mathrm{E}} \cdot \overrightarrow{\mathrm{A}}=0$ the lines are parallel to the surface.

Topic: Physics, Electrostatics, NEET, NEET 2010 (Screening)
A square surface of side $L$ metres is in the plane of the paper. A uniform electric field $\vec{E}$ (volt $/ \mathrm{m})$, also in the plane of the paper, is limited only to the lower half of the square surface (see figure). The electric flux in SI units associated with the surface is:

Options:
A $E L^2$
B $E L^2 / 2 \varepsilon_{\text {o }}$
C $E L^2 / 2$
D zero

The correct answer is:
zero

Solution:
Electric flux $\phi_E=\int \vec{E} \cdot \overrightarrow{d s}=\int E d s \cos \theta$
$$
=\int E d s \cos 90^{\circ}=0 .
$$

Topic: Physics, Electrostatics, NEET, NEET 2006
A square wire frame of side a is placed a distance b away from a long straight conductor carrying current I. The frame has resistance R and self-inductance L. The frame is rotated by 180o about OO' as shown in Fig. Find the electric charge flown through the frame -

Options:
A 2μ0ia22πRb
B μ0i2πRloge⁡b+ab-a
C μ0ia2πRloge⁡b+ab-a
D None of these

The correct answer is:
μ0ia2πRloge⁡b+ab-a

Solution:
i=1Rdϕdt+Ldidt
q=∫idt=1R∆ϕ+0=∆ϕR=1R∫b-ab+aBadx
=1R∫b-ab+aμ0ia2πxdx=μ0ia2πRloge⁡b+ab-a

Topic: Physics, Electromagnetic Induction, NEET
A stable community is characterised by:

Options:
A Constant productivity
B Resistant to invasions by alien species
C High resilience
D All of the above

The correct answer is:
All of the above

Solution:
A stable community should not show too much variation in productivity from year to year; it must be either resistant or resilient to occasional disturbances (natural or man-made), and it must also be resistant to invasions by alien species. David Tilman’s long-term ecosystem experiments using outdoor plots provide some tentative answers. Tilman found that plots with more species showed less year-to-year variation in total biomass. He also showed that in his experiments, increased diversity contributed to higher productivity.

Topic: Biology, Biodiversity and its Conservation, NEET
A stage in cell division is shown in the figure. Select the answer which gives correct identification of the stage with its characteristics

Options:
A $$
\begin{aligned}
& \text { Telophase - Nuclear envelope } \\
& \text { reforms, Golgi complex } \\
& \text { reforms } \\
&
\end{aligned}
$$
B $$
\begin{aligned}
\text { Late } & \text { Chromosomes move } \\
\text { anaphase } & \text { away from equatorial } \\
& \text { plate, Golgi complex not } \\
& \text { present }
\end{aligned}
$$
C $$
\begin{aligned}
\text { Cytokinesis - } & \text { Cell plate formed, } \\
& \text { mitochondria distributed } \\
& \text { between two daughter } \\
& \text { cells }
\end{aligned}
$$
D $$
\begin{array}{cl}
\text { Telophase - Endoplasmic reticulum } \\
\text { and nucleolus not } \\
\text { reformedyet }
\end{array}
$$

The correct answer is:
$$
\begin{aligned}
& \text { Telophase - Nuclear envelope } \\
& \text { reforms, Golgi complex } \\
& \text { reforms } \\
&
\end{aligned}
$$

Solution:
Telophase is reserve of prophase. The chromosome that have reached their respective polar decondense and their individually. Late anaphase is characterised by centromeres split and chromatid separate and chromatid move to opposite poles. Cytokinesis is process in which cell itself is divided two daughter cells.

Topic: Biology, Cell Cycle and Cell Division, NEET, NEET 2013 (All India)
A stage of mitosis is shown in the diagram. Which stage is it and what are its characteristics?

Options:
A Metaphase - Spindle fibers attached to kinetochores, centromeres split and chromatids separate.
B Metaphase- Chromosomes moved to spindle equator, chromosomes made up of two sister chromatids.
C Anaphase- Centromeres split and chromatids separate and start moving away.
D Late prophase - Chromosomes move to spindle equator

The correct answer is:
Metaphase- Chromosomes moved to spindle equator, chromosomes made up of two sister chromatids.

Solution:
Prophase is marked by the initiation of condensation of chromosomal material. The chromosomal material becomes untangled during the process of chromatin condensation. Initiation of the assembly of mitotic spindle, the microtubules, the proteinaceous components of the cell cytoplasm help in the process. Metaphase is characterized by all the chromosomes coming to lie at the equator with one chromatid of each chromosome connected by its kinetochore to spindle fibres from one pole and its sister chromatid connected by its kinetochore to spindle fibres from the opposite pole.
Anaphase stage is characterised by following key events like Centromeres split and chromatids separate and Chromatids move to opposite poles. As each chromosome moves away from the equatorial plate, the centromere of each chromosome is towards the pole and hence at the leading edge, with the arms of the chromosome trailing behind.
Telophase is characterised by chromosomes cluster at opposite spindle poles and their identity is lost as discrete elements. Nuclear envelope assembles around the chromosome clusters. Nucleolus, Golgi complex and ER reform.
Stages of mitosis:

Topic: Biology, Cell Cycle and Cell Division, NEET, NEET 2013 (Karnataka)
A standing wave propagating with velocity 300 m s-1 in an open pipe of length 4 m has four nodes. The frequency of the wave is

Options:
A 75 Hz
B 100 Hz
C 150 Hz
D 300 Hz

The correct answer is:
150 Hz

Solution:
Nodes are produced in the open pipe as shown in figure.
So, 2λ=4
λ=42=2 m
From the wave equation,
v=nλ
n=vλ
=3002
=150 Hz

Topic: Physics, Waves and Sound, NEET
A star is moving away from Earth and shift in spectral line of wavelength 5700 â« is 1.90 â« . Velocity of the star is

Options:
A 50 km s-1
B 70Â kmÂ s-1
C 85Â kmÂ s-1
D 100Â kmÂ s-1

The correct answer is:
100 km s-1

Solution:
∆λ=υc λ
∴υ=c ∆λλ
Or υ=3×108×1.9×10-105700×10-10=100 km s-1

Topic: Physics, Waves and Sound, NEET
A star is moving away from earth with velocity of 100 km s-1. If the velocity of light is 3Ã108 m s-1 , then shift of the spectral line of Î»=5700 â« due to Doppler effect will be

Options:
A 1.90 â«
B 3.80Â â«
C 5.70Â â«
D None of these

The correct answer is:
1.90 â«

Solution:
In case of Dopplers effect in light waves
Using âÎ»=ÏcÃÎ»=105Ã57003Ã108=1.90 â«
âÎ»= shift to spectral line

Topic: Physics, Wave Optics, NEET
A stationary hydrogen atom in the first excited state emits a photon. If the mass of the hydrogen atom is m and its ionization energy is E, then the recoil velocity acquired by the atom is [speed of light = c]

Options:
A 3E2m+c2-c
B 3E4m+c2-c
C 3E4mc
D Emc

The correct answer is:
3E2m+c2-c

Solution:
mv=hλ, here v is recoil speed of H-atom and λ is the wavelength of the photon.

When the electron jumps down from the first excited state to the ground state the energy released is

∆E2→1=E1-122=3E4

3E4=12mv2+hcλ

3E4=12mv2+mvc

m2v2+mcv-3E4=0

⇒v=3E2m+c2-c

Topic: Physics, Atomic Physics, NEET
A stationary object at 4 °C and weighing 3.5 kg falls from a height of 2000 m on a snow mountain at 0 oC. If the temperature of the object just before hitting the snow is 0 oC and the object comes to rest immediately, then the object will melt (Use, g=10 m s-2 and latent heat of ice=3.5×105 J kg-1)

Options:
A 2Â kg of ice
B 200 g of ice
C 20Â g ice
D 2Â g of ice

The correct answer is:
200 g of ice

Solution:
Suppose m kg of ice melts then by using
W(Joules)=H(Joules)
Mgh=mL
3.5Ã10Ã2000=mÃ3.5Ã105
m=0.2 kg=200 g

Topic: Physics, Thermal Properties of Matter, NEET
A stationary object is released from a point P a distance 3R from the centre of the moon which has radius R and mass M. Which one of the following expressions gives the speed of the object on hitting the moon?

Options:
A 2GM3R12
B 4GM3R12
C 2GMR12
D GMR12

The correct answer is:
4GM3R12

Solution:
According to the law of conservation of energy,
-GmM3R+mv022=-GmMR+mv122
Where m is the mass of the object, v0 and v1 are the initial and final velocities of object, respectively.
The object is stationary i.e., v0=0.
â -GM3R=-GMR+v122
â v122=2GM3R
â v1=2GM3R=4GM3R12

Topic: Physics, Gravitation, NEET
A stationary particle explodes into two particles of masses $m_1$ and $m_2$ which more in opposite direction with velocities $v_1$ and $v_2$. The ratio of their kinetic energies $E_1 / E_2$ is:

Options:
A $m_2 / m_1$
B $m_1 / m_2$
C 1
D $m_1 m_2 / m_2 m_1$

The correct answer is:
$m_2 / m_1$

Solution:
According to law of conservation of linear momentum
$$
\begin{aligned}
& m_1 v_1=m_2 v_2 \quad \ldots \text { (i) } \\
& E_1=\frac{1}{2} m_1 v_1^2, E_2=\frac{1}{2} m_2 v_2^2 \\
& \therefore \frac{E_1}{E_2}=\frac{\frac{1}{2} m_1 v_1^2}{\frac{1}{2} m_2 v_1^2}=\frac{\left(m_1 v_1\right)^2}{\left(m_2 v_2\right)^2} \times \frac{m_2}{m_1} \\
& \therefore \frac{E_1}{E_2}=\frac{m_2}{m_1}
\end{aligned}
$$

Topic: Physics, Center of Mass Momentum and Collision, NEET, NEET 2003
A stationary pulley carries a rope one end of which supports a ladder with a man and the other a counterweight of mass M . The man of mass m climbs up a distance l with respect to the ladder and then stops. The displacement of the centre of mass of this system is

Options:
A mlM+m
B ml2M
C mlM+2m
D ml2M+m

The correct answer is:
ml2M

Solution:
From the question mass of the ladder is M-m .
Let's assume that counterweight goes up by distance x then ladder also goes down by x. Therefore from the ground frame, man goes up by l-x .
Then distance moved by the center of mass is given by,
xcm=Mx+ml-x+M-m-x2M
xcm=ml2M

Topic: Physics, Center of Mass Momentum and Collision, NEET
A stationary source (see figure) emits sound waves of frequency f towards a stationary wall. If an observer moving with speed u in a direction perpendicular to the wall measures a frequency f′=118f at the instant shown, then u is related to the speed of sound Vs as

Options:
A 34 Vs
B 38 Vs
C 14 Vs
D 83 Vs

The correct answer is:
34 Vs

Solution:
This is the case of Doppler's effect in reflected sound.
The apparent frequency is given by
f′=fv+v0v-vs
Given, f′=118f
v0=u
vs=0 (stationary source)
v=Vs
∴118f=vs+ucos⁡60Vs
118=1+u2Vs
38=u2Vs
Vs=43u

Topic: Physics, Waves and Sound, NEET
A statutory ban has been imposed on sex-determination because

Options:
A amniocentesis is an expensive procedure.
B it is morally inappropriate to determine the sex of the child.
C it accelerated the birth rate in the country.
D to check female foeticides in the country.

The correct answer is:
to check female foeticides in the country.

Solution:
Statutory ban on amniocentesis (a foetal sex determination test based on the chromosomal pattern in the amniotic fluid surrounding the developing embryo) for sex-determination has imposed to legally check increasing female foeticides, massive child immunisation, etc.

Topic: Biology, Reproductive Health, NEET
A steady current is set up in a metallic wire of non-uniform cross-section. The rate of flow of electrons (R) related to the area of cross-section (A)

Options:
A R∝A-1
B R∝A
C R∝A2
D R is independent of A

The correct answer is:
R∝A-1

Solution:
Rate of flow of electrons in a conductor is low but the number density of free electrons in a conductor is very high. The drifting of electrons over the entire length of the conductor contributes to the current throughout the conductor

Topic: Physics, Current Electricity, NEET
A steady current of $1.5 \mathrm{amp}$ flows through a copper voltameter for 10 minutes. If the electrochemical equivalent of copper is 30 $\times 10^{-5} \mathrm{~g}$ coulomb $^{-1}$, the mass of copper deposited on the electrode will be.

Options:
A $0.50 \mathrm{~g}$
B $0.67 \mathrm{~g}$
C $0.27 \mathrm{~g}$
D $0.40 \mathrm{~g}$.

The correct answer is:
$0.27 \mathrm{~g}$

Solution:
Given that $\mathrm{I}=1.5 \mathrm{~A} t=10 \mathrm{~mm}=600$ sec

and $z=30 \times 10^{-5} \mathrm{~g} \mathrm{~coulomb}^{-1}$
According to faraday first law of electrilysis
$\begin{aligned}
& m=Z I T=30 \times 10^{-5} \times 1.5 \times 600= \\
& 0.27 \mathrm{~g}
\end{aligned}$

Topic: Chemistry, Electrochemistry, NEET, NEET 2007