Practice Test - NEET MCQ

Explanation:

When a negatively charged conductor is connected to the earth, electrons will flow from the conductor to the earth. This is because electrons have a negative charge and they will be repelled from the negatively charged conductor and attracted to the positively charged earth. As electrons flow from the conductor to the earth, the negative charge on the conductor will gradually decrease until it becomes neutral.

• Option A is incorrect because charge flow does occur when a negatively charged conductor is connected to the earth.
• Option B is incorrect because protons have a positive charge and they are not free to move in a conductor.
• Option C is incorrect because electrons flow from the earth to the conductor, not the other way around.

As aluminium and copper are metals, their mobile electrons move under the influence of the external field until they reach the surface of the metal and collect there. External electric fields induce surface changes on metal objects that exactly cancel the field within. Since the field applied is same in both case, the induced charge will be the same.
Hence, the magnitude of induced charge in the aluminium will be the equal to that of copper.

In case I :


In Case II :


From equations (i) and (ii),

Let m be mass of each ball and q be charge on each ball. Force of repulsion,


In equilibrium
Tcosq = mg ...(i)
Tsinq = F ...(ii)
Divide (ii) by (i), we get,

From figure (a),



Divide (iv) by (iii), we get

Since the charge –q is moving in elliptical orbit so to make its motion stable the total angular momentum of the charge is constant since it experience a centripetal force from the charge +Q so it follow the motion as the motion of earth around sun.

Acceleration 

This consists of two dipoles, –q and +q with dipole moment along with the +y-direction and –q and +q along the x-direction.


Along the direction 45° that is along OP, where P is (+a, +a, 0).

The correct answer is option B.

The I.U.P.A.C. name for Fe(C₅H₅)₂ is bis(η⁵ -cyclopentadienyl) iron(II) 
The oxidation state of iron is +2 and is written in parenthesis in roman numerals. Two cyclopentadienyl ligands are coordinated to Fe. The prefix bis indicates 2. η⁵ indicates that the cyclopentadienyl ligands are penta coordinates.

Since both cation & anion constitute coordination sphere so it exhibit coordination isomerism and contains ambident ligand so, it shows linkage isomerism

O. N. of Al = +3
O. N. of B = + 3
[BF₄]^-
[Al(C₂O₃)₃]^3-

The correct answer is B: CNS⁻.

Explanation:

• Linkage isomerism occurs when a ligand can coordinate to the central metal ion through two different atoms, leading to different isomers.

• Flexidentate ligands are ligands that can form multiple bonds to the metal centre via different donor atoms.

CNS⁻ (Thiocyanate) is an example of a ligand that can exhibit linkage isomerism. The thiocyanate ion (CNS⁻) can bind to the metal through the nitrogen atom (N) or the sulfur atom (S), leading to two different isomers:

1. N-bonded thiocyanate (also called isothiocyanate),

2. S-bonded thiocyanate.

This makes CNS⁻ a flexidentate ligand, as it can coordinate through two different donor atoms (N or S), showing linkage isomerism.

Thus, the correct answer is B: CNS⁻.

Higher the value of K higher will be strength of ligand & more will be thermodynamic stability of complex produced.

• Gibberellic acid is a Terpene.
• All known gibberellins are diterpenoid acids that are synthesized by the terpenoid pathway in plastids and then modified in the endoplasmic reticulum and cytosol until they reach their biologically-active form.
• All gibberellins are derived via the ent-gibberellane skeleton, but are synthesized via ent-kaurene.

The following are plant growth regulators or phytohormones that control various developmental as well as physiological functions of a plant:

Auxin:

• It helps in cell elongation, growth, and differentiation.
• It is present mainly at the root and shoots apices.
• It is responsible for the phenomenon of apical dominance, where the apical buds inhibit the growth of lateral buds.
• It results in increasing the height of a plant due to apical dominance.
• It can also initiate root growth in stem cuttings.
• It may also promote flowering and prevent early fruit drop.

Cytokinin:

• It is mainly associated with cell division and is present in regions of rapid cell division.
• It helps to overcome apical dominance and promotes lateral shoot growth.

Ethylene:

• It is a gaseous phytohormone produced in the tissues undergoing senescence.
• It helps in fruit ripening and other senescence-related activities.
• It breaks seed and bud dormancy to initiate germination in some species.
• It also induces leaf epinasty under stress conditions.
• The triple response of ethylene includes reducing the rate of elongation, increasing lateral expansion, and swelling of the region below the hook in seedlings.

Abscisic acid:

• As the name suggests, it helps in abscission and dormancy.
• It inhibits plant growth, metabolism, and seed germination.
• It also plays an important role in the closure of stomata under stress conditions.

The plant hormone auxin is used for agriculture and horticulture.

• During the process of plant propagation, auxin is used to initiate rooting in stem cutting.
• Auxin performs the role of promoting flowering in the plant.
• Abscission of older mature fruits and leaves is regulated by the hormone auxin.
• It also prevents leaves and fruits from dropping at the early stage. The growing apical buds in most higher plants inhibit the growth of auxiliary buds. This phenomenon is called apical dominance.

Therefore, the correct answer is option D.

Stem elongation is a kind of growth of stem.

Auxin and Gibberellin are known as growth hormones of plants. Therefore, stem elongation is affected by hormones Auxin and Gibberellin.

Microtubules are unbranched hollow tubules of indefinite length about 25 nm of thickness with 15 nm core and boundary formed of 13 helically arranged protofilaments of globular molecules of α and β tubulins. Microtubules grow from nucleating regions. Their tips can grow and shorten quickly. 
Microfilaments are double helical cylindrical rods or filaments of actin-like protein that occur in both muscular and nonmuscular eukaryotic cells.
As microtubules do not radiate out from ER as they radiate out from the centrioles during cell division.

So, the correct answer is option C.

Most skeletal muscles are attached to bones by bundles of collagen fibers known as tendons. A skeletal muscle refers to multiple bundles (fascicles) of cells joined together called muscle fibers. The fibers and muscles are surrounded by connective tissue layers called fasciae.

Hinge joint occurs between humerus and radioulnar.
A hinge joint is a common class of synovial joint that includes the ankle, elbow and knee joints. Hinge joints are formed between two or more bones where the bones can only move along one axis to flex or extend. The elbow is a hinged joint made up of three bones which are the humerus, ulna and radius.

Myology is the branch of biological science in which different aspects of muscles are studied.

Synovial joints are characterised by the presence of a fluid filled synovial cavity between the articulating surfaces of the two bones. Saddle joint (between carpal and metacarpal of thumb)

Trachea divides at the level of 5th thoracic vertebra into a right and left primary bronchi.

After a forceful expiration gaseous exchange continues uninterrupted because there is always a residual volume of air that continues the diffusion of gasese.

Figure 1 represents the alveoli of healthy person and figure 2 is the alveoli of emphysema patient. The wall of alveoli is get damaged in figure 2 to reduce the surface area for exchange of gases.

• The nodal musculature has the ability to generate action potentials without any external stimuli.
• The number of action potentials that could be generated in a minute varies at different parts of the nodal system.
• The SAN can generate the maximum number of action potentials and is responsible for initiating and maintaining the rhythmic contractile activity of the heart.
• Therefore, it is called the pacemaker.

• Platelets, also called thrombocytes, are cell fragments produced from megakaryocytes.
• Platelets can release a variety of substances most of which are involved in the coagulation or clotting of blood.

The hepatic portal vein carries blood from the intestine to the liver before it is delivered to the systemic circulation.

A special case of Rh incompatibility (mismatching) has been observed between the Rh^-ve blood of a pregnant mother with Rh^+ve blood of the foetus.