# A thin flat circular disc of radius $$4.5~\text {cm}$$ is placed gently over the surface of water. If surface tension of water is $$0.07~\text{Nm}^{-1},$$ then the excess force required to take it away from the surface is: 1. $$198~\text{N}$$ 2. $$1.98~\text{mN}$$ 3. $$99~\text{N}$$ 4. $$19.8~\text{mN}$$

Subtopic:  Surface Tension |
From NCERT
NEET - 2024
Hints

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
 Assertion (A): The potential $$(V)$$ at any axial point, at $$2~\text m$$  distance ($$r$$) from the centre of the dipole of dipole moment vector $$\vec P$$ of magnitude, $$4\times10^{-6}~\text{C m},$$ is $$\pm9\times10^3~\text{V}.$$ (Take $${\dfrac{1}{4\pi\varepsilon_0}}=9\times10^9$$ SI units) Reason (R): $$V=\pm{\dfrac{2P}{4\pi\varepsilon_0r^2}},$$ where $$r$$ is the distance of any axial point situated at $$2~\text m$$ from the centre of the dipole.
In the light of the above statements, choose the correct answer from the options given below:
 1 Both (A) and (R) are True and (R) is not the correct explanation of (A). 2 (A) is True but (R) is False. 3 (A) is False but (R) is True. 4 Both (A) and (R) are True and (R) is the correct explanation of (A).
Subtopic:  Electric Potential |
51%
From NCERT
NEET - 2024
Hints

In a uniform magnetic field of $$0.049~\text T$$, a magnetic needle performs $$20$$ complete oscillations in $$5$$ seconds as shown. The moment of inertia of the needle is $$9.8 × 10^{-6} ~\text{kg m}^2$$. If the magnitude of magnetic moment of the needle is $$x \times 10^{-5 }~\text {Am}^2;$$ then the value of '$$x$$' is:

1. $$128\pi^2$$
2.  $$50\pi^2$$
3. $$1280\pi^2$$
4. $$5\pi^2$$
Subtopic:  Bar Magnet |
From NCERT
NEET - 2024
Hints

If the monochromatic source in Young's double slit experiment is replaced by white light, then:
 1 there will be a central dark fringe surrounded by a few coloured fringes. 2 there will be a central bright white fringe surrounded by a few coloured fringes. 3 all bright fringes will be of equal width. 4 interference pattern will disappear.
Subtopic:  Young's Double Slit Experiment |
57%
From NCERT
NEET - 2024
Hints

Given below are two statements:
 Statement I: Atoms are electrically neutral as they contain equal number of positive and negative charges. Statement II: Atoms of each element are stable and emit their characteristic spectrum.

In the light of the above statements, choose the most appropriate answer from the options given below:
 1 Both Statement I and Statement II are incorrect. 2 Statement I is correct but Statement II is incorrect. 3 Statement I is incorrect but Statement II is correct. 4 Both Statement I and Statement II are correct.
Subtopic:  Spectral Series |
From NCERT
NEET - 2024
Hints

The maximum elongation of a steel wire of $$1~\text m$$ length if the elastic limit of steel and its Young's modulus, respectively, are $$8 × 10^8 ~\text{N m}^{-2 }$$ and $$2 × 10^{11} ~\text{N m}^{-2},$$ is:
1. $$0.4~\text{mm}$$
2. $$40~\text{mm}$$
3. $$8~\text{mm}$$
4. $$4~\text{mm}$$
Subtopic:  Young's modulus |
66%
From NCERT
NEET - 2024
Hints

Consider the following Statements A and B and identify the correct answer:

 A. For a solar-cell, the $$I\text-V$$ characteristics lies in the IV quadrant of the given graph. B. In a reverse-biased pn junction diode, the current measured in ($$\mu \text{A}$$), is due to majority charge carriers.

 1 A is incorrect but B is correct. 2 Both A and B are correct. 3 Both A and B are incorrect. 4 A is correct but B is incorrect.
Subtopic:  Applications of PN junction |
From NCERT
NEET - 2024
Hints

A particle moving with uniform speed in a circular path maintains:
 1 constant acceleration. 2 constant velocity but varying acceleration. 3 varying velocity and varying acceleration. 4 constant velocity.
Subtopic:  Circular Motion |
58%
From NCERT
NEET - 2024
Hints

If $$c$$ is the velocity of light in free space, the correct statements about photon among the following are:
 A. The energy of a photon is $$E=h\nu.$$ B. The velocity of a photon is $$c.$$ C. The momentum of a photon, $$p={\dfrac{h\nu}{c}}.$$ D. In a photon-electron collision, both total energy and total momentum are conserved. E. Photon possesses positive charge.
Choose the correct answer from the options given below:
1. $$\text {A, B, C}$$ and $$\text {D}$$ only
2. $$\text {A, C}$$ and $$\text {D}$$ only
3. $$\text {A, B, D}$$ and $$\text {E}$$ only
4. $$\text {A}$$ and $$\text {B}$$ only
Subtopic:  Particle Nature of Light |
56%
From NCERT
NEET - 2024
Hints

Two bodies $$A$$ and $$B$$ of same mass undergo completely inelastic one dimensional collision. The body $$A$$ moves with velocity $$v_1$$ while body $$B$$ is at rest before collision. The velocity of the system after collision is $$v_2$$. The ratio $$v_1:v_2$$ is:
1. $$2:1$$
2. $$4:1$$
3. $$1:4$$
4. $$1:2$$
Subtopic:  Collisions |
63%
From NCERT
NEET - 2024