datavorous/entrance-exam-dataset huggingface dataset:
The ‘lock’ and ‘key’ model of enzyme action illustrates that a particular enzyme molecule

Options:
A maybe destroyed and resynthesised several times
B interacts with a specific type of substrate molecule
C reacts at identical rates under all conditions
D forms a permanent enzyme-substrate complex

The correct answer is:
interacts with a specific type of substrate molecule

Solution:
Emil Fisher (1894) proposed ‘lock and key theory’ for the mechanism of enzyme action, according to which the active sites of the enzyme have a specific geometric shape wherein the substrate molecules fit in just like a key in a particular lock. In other words, it illustrates that a particular enzyme molecule interacts with a specific type of substrate molecule.

Topic: Chemistry, Biomolecules, NEET
The "lock and key" model of enzyme action illustrates that a particular enzyme molecule:

Options:
A May be destroyed and resynthesised several times
B Interacts with a specific type of substrate molecule
C Reacts at identical rates under all conditions
D Forms a permanent enzyme-substrate complex

The correct answer is:
Interacts with a specific type of substrate molecule

Solution:
Lock and key theory was proposed by Emil Fischer it states that each enzyme molecule has a specific active site to which only a specific substrate can fit and bind forming ES complex. It thus explains that each enzyme molecule interacts with a specific type of substrate only.

Topic: Chemistry, Biomolecules, NEET
The ‘lock’ and ‘key’ model of enzyme action illustrates that a particular enzyme molecule

Options:
A May be destroyed and resynthesised several times
B Interacts with a specific type of substrate molecule
C Reacts at identical rates under all conditions
D Forms a permanent enzyme-substrate complex

The correct answer is:
Interacts with a specific type of substrate molecule

Solution:
Emil Fisher (1894) proposed ‘lock and key theory’ for the mechanism of enzyme action, according to which the active sites of the enzyme have a specific geometric shape wherein the substrate molecules fit in just like a key in a particular lock. In other words, it illustrates that a particular enzyme molecule interacts with a specific type of substrate molecule.

Topic: Chemistry, Biomolecules, NEET
The logic circuit shown below has the input waveforms ′A′ and ′B′, as shown. Pick out the correct output waveform

Output is :

Options:
A
B
C
D

The correct answer is:

Solution:
The output will be of AND gate.
The output will be high only when both the inputs are high.

Topic: Physics, Semiconductors, NEET
The logic circuit shown below has the input waveforms A and B as shown. Pick out the correct output waveform.
â

Options:
A
B
C
D

The correct answer is:

Solution:
The output will be of AND gate.

The output will be high only when both the inputs are high.

Topic: Physics, Semiconductors, NEET
The logic circuit shown has the input waveforms 'A' and 'B' as shown. Pick out the

CORRECT

output waveform : -

Options:
A

B
C
D

The correct answer is:

Solution:

Topic: Physics, Semiconductors, NEET
The logic gate given below represents a

Options:
A NAND gate
B NOR gate
C OR gate
D AND gate

The correct answer is:
NAND gate

Solution:
Logic symbol of NAND gate:

Topic: Physics, Semiconductors, NEET
The logistic population growth is expressed by the equation:

Options:
A dt / dN = Nr ( K - Ν Kâ¡ )
B d N / d t = rN ( K - Ν Kâ¡ )
C d N / d t = rN
D d N / d t = rN ( N&ApplyFunction; - K&ApplyFunction; N&ApplyFunction; )

The correct answer is:
d N / d t = rN ( K - Ν Kâ¡ )

Solution:
The logistic population growth is expressed
by the equation d N / d t = rN [ ( Kâ¡ - Nâ¡ ) Kâ¡ ]
Where N is population density at time t, r is the Malthusian parameter (rate of maximum population growth) and K is the so called carrying capacity (i.e. maximum sustainable population). It is a type of population growth when resources are limiting.

Topic: Biology, Organisms and Populations, NEET
The longest bone in the human body is

Options:
A A triangular flat bone situated in the dorsal part of the thorax
B A long slender bone with two curvatures
C A bone situated in the lower extremity which takes part in formation of knee joint
D A coxal bone

The correct answer is:
A bone situated in the lower extremity which takes part in formation of knee joint

Solution:
The longest and strongest bone in the human body is the femur. It is situated in the lower extremities i.e. in the thigh. It takes part in the formation of knee joint along with patella and tibia.

Topic: Biology, Locomotion and Movement, NEET
The longest bone of the human body is:

Options:
A Humerus
B Tibia
C Vertebra
D Femur

The correct answer is:
Femur

Solution:
In humans, femur or the thigh bone is the longest bone of the body. It articulates with the acetabulum to form the hip joint.

Topic: Biology, Locomotion and Movement, NEET
The longest part of the fallopian tube is

Options:
A Isthmus
B Fimbriated end
C Ampulla
D Uterine part of Fallopian tube.

The correct answer is:
Ampulla

Solution:
Parts of the fallopian tube:
a. Infundibulum - It is a funnel-shaped part and is closer to the ovary. Fimbriae: These are the finger-like projections at the edges of the infundibulum, which help in the collection of the ovum after ovulation.
b. Ampulla: The infundibulum leads to ampulla which is the wider and longest part of the oviduct. It is also the most common site for fertilization
c. Isthmus: It is the last part of the oviduct that joins the uterus. It possesses a narrow lumen.

Topic: Biology, Human Reproduction, NEET
The longest wavelength doublet absorption transition is observed at 589 and 589.6 nm. Which of the options is closest to the energy difference between two excited states?

Options:
A 4.7 × 10–22J
B 3.4 × 10–22J
C 6.9 × 10–22J
D 7.6 × 10–22J

The correct answer is:
3.4 × 10–22J

Solution:
Correct Option is : (B)
3.4 × 10–22J

Topic: Chemistry, Structure of Atom, NEET
The lower end of a glass capillary tube is dipped in water. Water rises to a height of 9 cm. The tube is then broken at a height of 5 cm. The height of the water column and angle of contact will be

Options:
A 5 cm, cos-1⁡59
B 4 cm, cos-1⁡54
C 5 cm, cos-1⁡95
D 5 cm, cos-1⁡67

The correct answer is:
5 cm, cos-1⁡59

Solution:
When a capillary tube is broken at a height 5 cm, meaning that water will rise to height 5 cm, hence h2=5 cm.
Since, we know, for capillarity phenomenon h=2Scosθrρg, where symbols have their usual meaning.
or hcosθ= constant
Thus, h1cosθ1=h2cosθ2
⇒9cosθ=5cosθ2 [for glass θ1=0 ]
⇒cosθ2=59 ∵ cos0o=1
∴θ2=cos-159

Topic: Physics, Mechanical Properties of Fluids, NEET
The luminosity of the Rigel star is 17000 times that of the sun. Assume both to be perfectly black bodies. If the surface temperature of the sun is 6000 K, then the temperature of the star is around (Take 1700014=11.4)

Options:
A 68400 K
B 58400 K
C 38600 K
D 32600 K

The correct answer is:
68400 K

Solution:
Luminosity of a star depends upon the total radiations emitted by the star.
The star emits 17000 times the radiations emitted by the sun.
â´ E=ÏT4
Hence, E1E=T1T4
So, 170001/4=T1T (Given, E1=17000E)
T1=6000Ã11.4=68400 K

Topic: Physics, Thermal Properties of Matter, NEET
The luteal phase in the menstrual cycle of primate female is also called

Options:
A secretory phase and lasts for about 13-14 days
B follicular phase and lasts for about 6-7 days
C proliferative phase and lasts for about 13-14 days
D secretory phase and lasts for about 6-7days

The correct answer is:
secretory phase and lasts for about 13-14 days

Solution:
The menstrual cycle has three important phases- (i) Follicular or proliferative phase, which lasts for about 7-9 days and is a highly variable phase. (ii) Ovulatory phase, the egg ruptures from the ovary on 14th day. (iii) Secretory phase, which lasts for about 13-14 days till the corpus luteum is survived and is the most constant phase.

Topic: Biology, Human Reproduction, NEET
The lymph collected from the body finally enters

Options:
A sub-clavian artery which is situated just below the heart
B sub-clavian artery which is situated above the heart
C sub-clavian vein which is situated just below the heart
D sub-clavian vein which is situated above the heart

The correct answer is:
sub-clavian vein which is situated above the heart

Solution:
As the blood passes through the capillaries some amount of it oozes out in the surrounding tissues. This is known as tissue fluid or interstitial fluid. When this fluid enters the lymphatic system it is known as lymph. Lymph is a colorless fluid as it lacks hemoglobin. It contains cells known as lymphocytes which is important for the immune system. The lymphatic system consists of lymphatic capillaries, nodes, vessels, and ducts. The lymphatic capillaries join to form lymphatic vessels. Large lymphatic vessels finally pour into one of the two principal vessels: Thoracic duct or right lymphatic duct. The thoracic duct receives lymph from the entire left side of the body. These two finally open into left and right sub-clavian veins.

Topic: Biology, Body Fluids and Circulation, NEET
The lymphoid organ which provides the micro-environments for the development and maturation of T-lymphocytes is

Options:
A bone marrow
B thymus
C spleen
D both a and b

The correct answer is:
both a and b

Solution:
The primary lymphoid organ such as bone marrow and thymus provide the micro-environments for the development and maturation of T-lymphocytes. Here the immature lymphocytes differentiate into antigen-sensitive lymphocytes.

Topic: Biology, Human Health and Diseases, NEET
The machine gun fires 240 bullets per minute. If the mass of each bullet is 10 g and the velocity of the bullets is 600 m s-1,the power (in kW)of the gun is

Options:
A 43200
B 432
C 72
D 7.2

The correct answer is:
7.2

Solution:
Work done by the gun
=Total kinetic energy of the bullets
=n=12mv2
=240Ã12Ã10Ã10-36002
=120Ã12Ã10Ã10-3Ã600Ã600
â´ Power of gun=work donetime taken
=120Ã10Ã10-3Ã600Ã6001min
=120Ã10Ã36060=120Ã10Ã6 W
120Ã10Ã61000 kW=7.2 kW

Topic: Physics, Work Power Energy, NEET
The macronutrient which is an essential component of cell organic compounds, yet not obtained by plants from soil, is

Options:
A Nitrogen
B Carbon
C Phosphorous
D Magnesium

The correct answer is:
Carbon

Solution:
Carbon, oxygen, and hydrogen are called the framework elements as all the components of a living organism contain C, H and O, particularly the carbohydrates, proteins, lipids and nucleic acids. The three elements are taken up by the plant in the form of CO2 and H2O.

Topic: Biology, Mineral Nutrition, NEET
The magnetic dipole moment of a current loop is independent of

Options:
A Magnetic field in which it is lying
B Number of turns
C Area of the loop
D Current in the loop

The correct answer is:
Magnetic field in which it is lying

Solution:
Magnetic dipole moment of a current is given by
M=IA
From the above relation it is clear that magnetic dipole moment of a current loop is independent of the magnetic field in which it is lying.

Topic: Physics, Magnetic Effects of Current, NEET
The magnetic dipole moment of a current loop is independent of

Options:
A Magnetic field in which it is lying
B Number of turns
C Area of the loop
D Current in the loop

The correct answer is:
Magnetic field in which it is lying

Solution:
Magnetic dipole moment of a current is given by
M=NIA
where N= number of turns
I= current in a loop
A= area of the loop
From the above relation, it is clear that magnetic dipole moment of a current loop is independent of the magnetic field in which it is lying.

Topic: Physics, Magnetic Effects of Current, NEET
The magnetic energy stored in an inductor of inductance 4 μH carrying a current of 2 A is:

Options:
A 8 μJ
B 4 μJ
C 4 mJ
D 8 mJ

The correct answer is:
8 μJ

Solution:
Magnetic energy stored in an inductor is given by,

U=12Li2=12×4×10-6×22=8×10-6 J=8 μJ

Topic: Physics, Electromagnetic Induction, NEET, NEET 2023 (All India)
The magnetic field at the centre (at nucleus) of the hydrogen-like atoms (atomic number = Z) due to the motion of an electron in nth orbit is proportional to

Options:
A n3Z5
B n4Z
C Z2n3
D Z3n5

The correct answer is:
Z3n5

Solution:
Bn=μ0In2rn
Or Bn ∝Inrn∝fn2rn
Bn ∝vnrnrn ∝vnrn2∝Znn2Z2∝Z3n5

Topic: Physics, Magnetic Effects of Current, NEET
The magnetic field at the origin due to the current flowing in the wire is

Options:
A -μ0I8πa i ^ + k ^
B μ 0 Iâ¡2πa i ^ + k ^
C μ0Iâ¡8πa - i ^ + k ^
D μ014πa2 i ^ - k ^

The correct answer is:
μ0Iâ¡8πa - i ^ + k ^

Solution:
B→=μ04πI2a(-i^+k^)2=μ0I8πa - i ^ + k ^

Topic: Physics, Magnetic Effects of Current, NEET
The magnetic field B due to a current-carrying circular loop of the radius 12 cm at its centre is 0.5Ã10â4 T. The magnetic field due to this loop at a point on the axis at a distance of 5 cm from the centre -

Options:
A 3.9 Ã 10â5 T
B 5.2Â ÃÂ 10â5Â T
C 2.1Â ÃÂ 10â5Â T
D 9Â ÃÂ 10â5Â T

The correct answer is:
3.9 Ã 10â5 T

Solution:
B0 =μ0I2a
At axial point
B=μ0Ia22 (a2+x2)3/2
BB0=a3(a2+x2)3/2
⇒ B= B0 a3(a2+x2)3/2
= 0.5 × 10–4 ×(12 cm)3(144 cm2+25 cm2)3/2
= 3.9 × 10–5 T.

Topic: Physics, Magnetic Effects of Current, NEET
The magnetic field due to current carrying circular coil loop of radius 6 cm at a point on axis at a distance of 8 cm from the centre is 54 Î¼T. What is the value at the centre of loop?

Options:
A 75 Î¼T
B 125Â Î¼T
C 150Â Î¼T
D 250Â Î¼T

The correct answer is:
250 μT

Solution:
Given, radius of coil, a=6 cm
=6Ã10-2 m
Distance, r=8 cm
=8Ã10-2 m
Magnetic field on the axis of current (I) carrying coil,
B1=Î¼0Ia22a2+r23â2 ...(i)
Magnetic field on the centre of coil
B2=Î¼0I2a ...(ii)
Dividing Equation (ii) by Equation (i), we get
B2B1=Î¼0I2aÎ¼0Ia22a2+r23/2
=a2+r23/2a3
=6Ã10-22+8Ã10-223/26Ã10-23
â B2B1=4.63
B2=4.63ÃB1
=4.63Ã54 Î¼T
=250 Î¼T

Topic: Physics, Magnetic Effects of Current, NEET
The magnetic field due to current carrying circular loop of the radius 12 cm at its centre is 0.50Ã10-4 T. The magnetic field due to this loop at a point on the axis at a distance of 5 cm from the centre is

Options:
A 3.5Ã10-9 T
B 5.3Ã10-9 T
C 9.3Ã105 T
D 3.9Ã10-5 T

The correct answer is:
3.9Ã10-5 T

Solution:
Use BaxisBcentre=R2R2+x23/2
Baxis0.5×10-4=122122+523/2
Baxis=0.5×10-4 12133
Baxis=3.5×10-5 T

Topic: Physics, Magnetic Effects of Current, NEET
The magnetic field in a travelling electromagnetic wave has a peak value of 20 nT. The peak value of electric field strength is

Options:
A 3 V m-1
B 6 V m-1
C 9 V m-1
D 12 V m-1

The correct answer is:
6 V m-1

Solution:
From question, B0=20 nT=20×10−9 T
E0=B0C
E0=20×10−9×3×108=6 V m-1.
( ∵ velocity of light in vacuum C=3×108 m s−1)

Topic: Physics, Electromagnetic Waves, NEET
The magnetic field of a given length of wire for a single turn coil at the centre is ' $B$ ' then, its value for two turns coil for the same wire is:

Options:
A $\frac{B}{4}$
B $\frac{B}{2}$
C $4 B$
D $2 B$

The correct answer is:
$4 B$

Solution:
Here $B_1=B=\frac{\mu_0 I}{2 R}$
$\begin{aligned}
& B_2=\frac{\mu_0(2 \mathrm{I})}{2 r} \\
& \therefore 2 \times 2 \pi r=2 \pi R \Rightarrow r=R / 2
\end{aligned}$
So, $B_2 = 4 B$

Topic: Physics, Magnetic Effects of Current, NEET, NEET 2002
The magnetic field of a plane electromagnetic wave is given by $\overrightarrow{\mathrm{B}}=3 \times 10^{-8} \cos \left(1.6 \times 10^3 x+\right.$ $48 \times 10^{10}$ t) $\hat{j}$, then the associated electric field will be:

Options:
A $3 \times 10^{-8} \cos \left(1.6 \times 10^3 x+48 \times 10^{10} t\right) \hat{i} / \mathrm{m}$
B $3 \times 10^{-8} \sin \left(1.6 \times 10^3 x+48 \times 10^{10} t\right) \hat{i} / \mathrm{m}$
C $9 \sin \left(1.6 \times 10^3 x-48 \times 10^{10} t\right) \hat{k} \mathrm{~V} / \mathrm{m}$
D $9 \cos \left(1.6 \times 10^3 x+48 \times 10^{10} t\right) \hat{k} \mathrm{~V} / \mathrm{m}$

The correct answer is:
$9 \cos \left(1.6 \times 10^3 x+48 \times 10^{10} t\right) \hat{k} \mathrm{~V} / \mathrm{m}$

Solution:
Given, $\mathrm{B}=3 \times 10^{-8} \cos \left(1.6 \times 10^3 x\right.$ $\left.+48 \times 10^{10} t\right)$
On comparing equations (1) & (2), we get;
$\begin{aligned}
\mathrm{B}_0 & =3 \times 10^{-8} \\
c & =\frac{\omega}{k}=\frac{48 \times 10^{10}}{1.6 \times 10^3} \\
& =3 \times 10^8
\end{aligned}$
And also, $c=\frac{\mathrm{E}_0}{\mathrm{~B}_0}$
Hence, $E_0=B_0 \times c$
$\begin{aligned}
& =3 \times 10^{-8} \times 3 \times 10^8 \\
& =9
\end{aligned}$
So, the required equation is:
$\mathrm{E}=9 \cos \left(1.6 \times 10^3 x+48 \times 10^{10} t\right)$

Topic: Physics, Electromagnetic Waves, NEET, NEET 2022 (Phase 2)
The magnetic field on the axis at a distance z from the centre of the bar magnet would be?

Options:
A In the direction of the magnetic dipole moment M→ of the magnet
B In the opposite direction of the magnetic dipole moment M→ of the magnet
C In the perpendicular direction of the magnetic moment M→ of the magnet
D Its direction depends on the magnitude of the magnetic moment M→ of the magnet

The correct answer is:
In the direction of the magnetic dipole moment M→ of the magnet

Solution:
Magnetic field on the axis is in direction of magnetic dipole moment

Topic: Physics, Magnetic Properties of Matter, NEET
The magnetic field on the axis of a circular loop of radius $100 \mathrm{~cm}$ carrying current $I=\sqrt{2} \mathrm{~A}$, at point $1 \mathrm{~m}$ away from the centre of the loop is given by:

Options:
A $3.14 \times 10^{-7} \mathrm{~T}$
B $6.28 \times 10^{-7} \mathrm{~T}$
C $3.14 \times 10^{-4} \mathrm{~T}$
D $6.28 \times 10^{-4} \mathrm{~T}$

The correct answer is:
$3.14 \times 10^{-7} \mathrm{~T}$

Solution:
As per question, we have;
$\begin{aligned}
\mathrm{B} & =\mathrm{B}_0 \sin ^3 \theta \\
& =\frac{\mu_0 \mathrm{I}}{2 \pi} \sin ^3\left(45^{\circ}\right) \\
& =\frac{4 \pi \times 10^{-7} \times \sqrt{2}}{2 \times 1}\left(\frac{1}{\sqrt{2}}\right)^3 \\
& =3.14 \times 10^{-7} \mathrm{~T}
\end{aligned}$

Topic: Physics, Magnetic Effects of Current, NEET, NEET 2022 (Phase 2)
The magnetic flux linked to a circular coil of radius $R$ is:
$\phi=2 t^3+4 t^2+2 t+5 \mathrm{~Wb}$
The magnitude of induced emf in the coil at $t=5 \mathrm{~s}$ is:

Options:
A $108 \mathrm{~V}$
B $197 \mathrm{~V}$
C $150 \mathrm{~V}$
D $192 \mathrm{~V}$

The correct answer is:
$192 \mathrm{~V}$

Solution:
Given:
$\phi=2 t^3+4 t^2+2 t+5,$
& $t=5 \mathrm{~s}$
By Faraday's law of EMI, we have,
$\mathrm{emf}=-\frac{d \phi}{d t}$
(where, the symbols have their usual meanings)
$\begin{aligned}
e=\left|\frac{d \phi}{d t}\right| & =\left|\frac{d}{d t}\left(2 t^3+4 t^2+2 t+5\right)\right| \\
& =6 t^2+8 t+2
\end{aligned}$
$\begin{aligned}
ext{At } t & =5 s \\
e & =6(5)^2+8(5)+2 \\
& =192 \mathrm{~V}
\end{aligned}$

Topic: Physics, Electromagnetic Induction, NEET, NEET 2022 (Phase 2)
The magnetic flux linked with a coil (in Wb) is given by the equation ϕ=5t2+3t+16. The magnitude of induced emf in the coil at the fourth second will be:

Options:
A 33 V
B 43 V
C 108 V
D 10 V

The correct answer is:
43 V

Solution:
Given magnetic flux in terms of time, ϕ=5t2+3t+60, and we know that from Faraday's law of electromagnetic induction, rate of change of flux is directly related to induced EMF of the coil,

⇒|ε|=dϕdt=10t+3

At t=4 s, |ε|=40+3=43 V

Topic: Physics, Electromagnetic Induction, NEET, NEET 2020 (Phase 2)
The magnetic flux linked with a coil is ϕ and the EMF induced in it is Ε, then

Options:
A If Ï=0, Î must be 0
B If ϕ≠0, Ε cannot be zero
C If Ε is not 0, ϕ may or may not be 0
D none of the above is correct

The correct answer is:
If Ε is not 0, ϕ may or may not be 0

Solution:
Induced emf,
Ε=-dϕdt
Therefore, Ε=0 when dϕdt=0 and vice versa.
Even if ϕ=0,dϕdt may be non-zero.
Similarly, if ϕ≠0,dϕdt may be zero.
For example, if ϕ=ϕ0sinωt
Then, Ε=-dϕdt=-ϕ0cosωt

Topic: Physics, Electromagnetic Induction, NEET
The magnetic flux near the axis and inside the air-core solenoid of length 60 cm carrying current I is 1.57Ã106 Wb. Its magnetic moment will be (cross-sectional area of a solenoid is very small as compared to its length, Î¼0=4ÏÃ10-7 SI units)

Options:
A 0.25 A m2
B 0.5 A m2
C 0.75 A m2
D 1 A m2

The correct answer is:
0.75 A m2

Solution:
Magnetic induction inside the solenoid
B=Î¼0NIL
Magnetic flux, Ï=BA
=Î¼0 NI.AL
Magnetic moment =NIA=ÏLÎ¼0
=1.57Ã10-6Ã0.64Ã3.14Ã10-7
=0.75 A m2

Topic: Physics, Electromagnetic Induction, NEET
The magnetic flux through a circuit of resistance $R$ changes by an amount $\Delta \phi$ in a time $\Delta t$. Then the total quantity of electric charge $Q$ that passes any point in the circuit during the time $\Delta \mathrm{t}$ is represented by:

Options:
A $\mathrm{Q}=\frac{1}{R} \cdot \frac{\Delta \phi}{\Delta t}$
B $Q=\frac{\Delta \phi}{R}$
C $Q=\frac{\Delta \phi}{\Delta t}$
D $Q=R \cdot \frac{\Delta \phi}{\Delta t}$

The correct answer is:
$Q=\frac{\Delta \phi}{R}$

Solution:
According to the question on induced emf is:
$$
\begin{aligned}
& \text { and current } I=\frac{Q}{\Delta t}=\frac{\Delta \phi}{\Delta t} \cdot \frac{1}{R} \\
& \Rightarrow \quad q=\frac{\Delta \phi}{R}
\end{aligned}
$$

Topic: Physics, Electromagnetic Induction, NEET, NEET 2004
The magnetic flux through a coil varies with time as Ï=5t2+6t+9 . The ratio of emf at

t=3 s to t=0 s will be

Options:
A 9Â :Â 1
B 1Â :Â 6
C 6 :1
D 1Â :9

The correct answer is:
6 :1

Solution:
EMF is Îµ=-dÏdt
Îµ=-10t+6 V
At t=3s Îµ1=-36 V
At t=0s Îµ2=-6 V
Îµ1Îµ2=-36-6
Îµ1Îµ2=6

Topic: Physics, Electromagnetic Induction, NEET
The magnetic flux through a coil varies with time as Ï=5t-6t+9. The ratio of E.M.F. at t=0 s to t=0.5 s will be

Options:
A 9:1
B 1:6
C 6:1
D 1:9

The correct answer is:
6:1

Solution:
E=-dϕdt
E=-ddt5t-6t+9
E=6-10 t
t=0s,⁡E0=6-0=6 V
t=0.5s,⁡E0.5=6-5=1 V
E0E0.5=61

Topic: Physics, Electromagnetic Induction, NEET
The magnetic force acting on a charged particle of charge $-2 \mu \mathrm{C}$ in a magnetic field of $2 \mathrm{~T}$ acting in $y$ direction, when the particle velocity is $(2 \hat{\mathrm{i}}+3 \hat{\mathrm{j}}) \times 10^6 \mathrm{~ms}^{-1}$ is

Options:
A $8 \mathrm{~N}$ in $-\mathrm{z}$ direction
B $4 \mathrm{~N}$ in $z$ direction
C $8 \mathrm{~N}$ in $y$ direction
D $8 \mathrm{~N}$ in $z$ direction

The correct answer is:
$8 \mathrm{~N}$ in $-\mathrm{z}$ direction

Solution:
Key Idea: When a charge q moves with velocity $\vec{v}$ inside magnetic field of strength $\overrightarrow{\mathrm{B}}$, then force on charge is called magnetic Lorentz force. The magnetic Lorentz force is in the direction of vector $\overrightarrow{\mathrm{v}} \times \overrightarrow{\mathrm{B}}$
$$
\begin{aligned}
& \text { Magnetic Lorentz force } \overrightarrow{\mathrm{F}}=q(\overrightarrow{\mathrm{v}} \times \overrightarrow{\mathrm{B}}) \\
&=-2 \times 10^{-6}\left[2 \times 2 \times 10^6\right] \\
&=8 \mathrm{~N} \text { along negative -axis }
\end{aligned}
$$

Topic: Physics, Magnetic Effects of Current, NEET, NEET 2009 (Screening)
The magnetic induction field strength due to a short bar magnet at a distance 0.20 m on the equatorial line is 20Ã10-6 T. The magnetic moment of the bar magnet is

Options:
A 3.2 A m2
B 6.4 A m2
C 1.6 A m2
D 16 A m2

The correct answer is:
1.6 A m2

Solution:
B=μ04πMd3
20×10-6=10-7×M8×10-3
M=1.6×10-710-7=1.6 A m2

Topic: Physics, Magnetic Properties of Matter, NEET
The magnetic moment and moment of inertia of a magnetic needle as shown are, respectively, $1.0 \times 10^{-2} \mathrm{~A} \mathrm{~m}$ and $\frac{10^{-6}}{\pi^2} \mathrm{~kg} \mathrm{~m}^2$. If it completes 10 oscillations in 10 s , the magnitude of the magnetic field is

Options:
A 0.4 T
B 4 T
C 0.4 mT
D 4 mT

The correct answer is:
0.4 mT

Solution:
Time period of oscillation of magnet inside the magnetic field $T=2 \pi \sqrt{\frac{1}{M B}}$
$T=\frac{t}{n}=\frac{10}{10}=1 \mathrm{~s}$
$1=2 \pi \sqrt{\frac{10^{-6}}{\pi^2 \times 1.0 \times 10^{-2} \times B}}$
$\frac{1}{4}=\frac{10^{-4}}{B} \Rightarrow B=0.4 \mathrm{mT}$

Topic: Physics, Magnetic Properties of Matter, NEET, NEET 2024 (Re-NEET)