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NEET Full Mock Test: Practice Test 7

Question paper with answer key. Selection Pro

Q1. Two charges $+1\mu\text{C}$ and $+4\mu\text{C}$ are placed at a distance of $30\text{ cm}$ apart in air. At what distance from the $+1\mu\text{C}$ charge on the line joining them is the net electric field zero?
  1. $10\text{ cm}$
  2. $20\text{ cm}$
  3. $15\text{ cm}$
  4. $5\text{ cm}$

Answer: (A) $10\text{ cm}$

Neutral point distance $x = \frac{r}{\sqrt{\frac{q_2}{q_1}} + 1} = \frac{30}{\sqrt{\frac{4}{1}} + 1} = \frac{30}{2 + 1} = 10\text{ cm}$.

Q2. The threshold wavelength for photoelectric effect on a metal surface is $6000\ \text{\AA}$. The work function of the metal is approximately:
  1. $2.07\text{ eV}$
  2. $4.14\text{ eV}$
  3. $1.03\text{ eV}$
  4. $3.10\text{ eV}$

Answer: (A) $2.07\text{ eV}$

Work function $\phi = \frac{hc}{\lambda_0} = \frac{12400\text{ eV\cdot\AA}}{6000\text{\AA}} \approx 2.07\text{ eV}$.

Q3. A particle executes SHM with an amplitude $A$. At what displacement from its mean position is its kinetic energy equal to its potential energy?
  1. $\frac{A}{2}$
  2. $\frac{A}{\sqrt{2}}$
  3. $\frac{A}{4}$
  4. $\frac{\sqrt{3}A}{2}$

Answer: (B) $\frac{A}{\sqrt{2}}$

$ KE = PE \implies \frac{1}{2}m\omega^2(A^2 - x^2) = \frac{1}{2}m\omega^2 x^2 \implies A^2 - x^2 = x^2 \implies 2x^2 = A^2 \implies x = \frac{A}{\sqrt{2}}$.

Q4. An alternating voltage $V = 200\sqrt{2} \sin(100t)\text{ V}$ is applied across a $100\ \Omega$ resistor. The RMS current through the circuit is:
  1. $2\text{ A}$
  2. $2\sqrt{2}\text{ A}$
  3. $1\text{ A}$
  4. $\sqrt{2}\text{ A}$

Answer: (A) $2\text{ A}$

$V_{rms} = \frac{V_0}{\sqrt{2}} = \frac{200\sqrt{2}}{\sqrt{2}} = 200\text{ V}$. Current $I_{rms} = \frac{V_{rms}}{R} = \frac{200}{100} = 2\text{ A}$.

Q5. A body of mass $2\text{ kg}$ is dropped from a height of $10\text{ m}$. Ignoring air resistance, its kinetic energy just before hitting the ground is ($g = 9.8\text{ m/s}^2$):
  1. $196\text{ J}$
  2. $98\text{ J}$
  3. $392\text{ J}$
  4. $49\text{ J}$

Answer: (A) $196\text{ J}$

By conservation of mechanical energy, final $ KE = \text{initial } PE = mgh = 2 \times 9.8 \times 10 = 196\text{ J}$.

Q6. The self-inductance $L$ of a solenoid of length $l$, area of cross-section $A$, and total turns $N$ is given by:
  1. $\mu_0 \frac{N^2 A}{l}$
  2. $\mu_0 \frac{N A}{l}$
  3. $\mu_0 N^2 A l$
  4. $\mu_0 \frac{N A^2}{l}$

Answer: (A) $\mu_0 \frac{N^2 A}{l}$

Self-inductance of a solenoid is $L = \mu_0 n^2 A l = \mu_0 \left(\frac{N}{l}\right)^2 A l = \mu_0 \frac{N^2 A}{l}$.

Q7. The angle of minimum deviation for an equilateral glass prism is $30^\circ$. The refractive index of the material of the prism is:
  1. $\sqrt{2}$
  2. $1.5$
  3. $\sqrt{3}$
  4. $1.33$

Answer: (A) $\sqrt{2}$

For an equilateral prism, $A = 60^\circ$. Refractive index $ \mu = \frac{\sin\left(\frac{A + D_m}{2}\right)}{\sin\left(\frac{A}{2}\right)} = \frac{\sin\left(\frac{60^\circ + 30^\circ}{2}\right)}{\sin(30^\circ)} = \frac{\sin(45^\circ)}{\sin(30^\circ)} = \frac{1/\sqrt{2}}{1/2} = \sqrt{2}$.

Q8. The radius of gyration of a uniform circular disc of mass $M$ and radius $R$ about an axis passing through its center and perpendicular to its plane is:
  1. $\frac{R}{\sqrt{2}}$
  2. $\frac{R}{2}$
  3. $\frac{R}{\sqrt{3}}$
  4. $R$

Answer: (A) $\frac{R}{\sqrt{2}}$

Moment of inertia $I = \frac{1}{2} M R^2 = M K^2 \implies K = \frac{R}{\sqrt{2}}$.

Q9. Which of the following elements has the highest electronegativity on Pauling scale?
  1. Oxygen
  2. Chlorine
  3. Fluorine
  4. Nitrogen

Answer: (C) Fluorine

Fluorine is the most electronegative element in the periodic table with a Pauling value of 4.0.

Q10. The IUPAC name of $\text{CH}_3-\text{CH(OH)}-\text{CH}_2-\text{CHO}$ is:
  1. 3-hydroxybutanal
  2. 2-hydroxybutanal
  3. 3-hydroxybutan-2-one
  4. 4-hydroxybutan-2-one

Answer: (A) 3-hydroxybutanal

Numbering starts from the aldehyde carbon ($-\text{CHO}$ as C1). Hydroxyl group ($-\text{OH}$) is at C3, giving 3-hydroxybutanal.

Q11. The geometry and hybridization of $\text{XeF}_4$ molecule are respectively:
  1. Square planar and $sp^3d^2$
  2. Tetrahedral and $sp^3$
  3. Octahedral and $sp^3d^2$
  4. Square pyramidal and $sp^3d$

Answer: (A) Square planar and $sp^3d^2$

$\text{XeF}_4$ has 4 bond pairs and 2 lone pairs ($sp^3d^2$ hybridization). Its molecular geometry is square planar.

Q12. Which of the following metal ions gives a characteristic crimson red color in the flame test?
  1. Sodium
  2. Lithium
  3. Calcium
  4. Barium

Answer: (B) Lithium

Lithium imparts a crimson red color to the non-luminous flame.

Q13. Reaction of methyl magnesium bromide ($ CH_3MgBr$) with formaldehyde ($ HCHO$) followed by hydrolysis gives:
  1. Ethanol
  2. Methanol
  3. Propan-2-ol
  4. Ethanal

Answer: (A) Ethanol

Reaction of Grignard reagent with formaldehyde produces primary alcohols. $\text{HCHO} + \text{CH}_3\text{MgBr} \xrightarrow{\text{H}_3\text{O}^+} \text{CH}_3\text{CH}_2\text{OH}$ (ethanol).

Q14. What is the coordinate number of a face-centered cubic (fcc) unit cell?
  1. $6$
  2. $8$
  3. $12$
  4. $4$

Answer: (C) $12$

In an fcc or ccp lattice, each sphere touches 12 neighboring spheres (coordination number = 12).

Q15. According to Le Chatelier's principle, an exothermic reversible reaction is favored in the forward direction by:
  1. Increasing temperature
  2. Decreasing temperature
  3. Decreasing pressure
  4. Removing reactants

Answer: (B) Decreasing temperature

Exothermic reactions release heat; decreasing temperature shifts equilibrium in the forward direction according to Le Chatelier's principle.

Q16. Which polymer is commonly known as Teflon?
  1. Polytetrafluoroethylene (PTFE)
  2. Polyacrylonitrile (PAN)
  3. Polymethyl methacrylate (PMMA)
  4. Polyvinyl chloride (PVC)

Answer: (A) Polytetrafluoroethylene (PTFE)

Teflon is the commercial name for polytetrafluoroethylene ($[\text{CF}_2-\text{CF}_2]_n$).

Q17. The functional unit of inheritance made up of DNA sequence coding for RNA or polypeptide is called:
  1. Gene
  2. Cistron
  3. Muton
  4. Recon

Answer: (B) Cistron

A cistron is defined as a segment of DNA coding for a polypeptide chain.

Q18. Which plant growth regulator is commonly used to induce ripening of fruits?
  1. Auxin
  2. Gibberellin
  3. Ethylene
  4. Abscisic Acid

Answer: (C) Ethylene

Ethylene is a gaseous plant hormone that promotes fruit ripening and senescence.

Q19. During meiotic division, crossing over between non-sister chromatids occurs during:
  1. Leptotene
  2. Zygotene
  3. Pachytene
  4. Diplotene

Answer: (C) Pachytene

Crossing over occurs during the pachytene stage of prophase-I in meiosis.

Q20. In angiosperms, double fertilization results in the formation of:
  1. Zygote and Primary Endosperm Nucleus (PEN)
  2. Zygote and Synergid
  3. Endosperm and Seed Coat
  4. Embryo sac and Antipodals

Answer: (A) Zygote and Primary Endosperm Nucleus (PEN)

Syngamy yields a diploid zygote, and triple fusion yields a triploid primary endosperm nucleus (PEN).

Q21. Which of the following ecosystems shows an inverted pyramid of biomass?
  1. Grassland ecosystem
  2. Forest ecosystem
  3. Pond ecosystem
  4. Desert ecosystem

Answer: (C) Pond ecosystem

In aquatic/pond ecosystems, biomass of standing crop of phytoplankton is small compared to zooplankton/fish, giving an inverted pyramid.

Q22. The primary cause of biodiversity loss worldwide, often called the 'Evil Quartet' chief component, is:
  1. Habitat loss and fragmentation
  2. Over-exploitation
  3. Alien species invasions
  4. Co-extinctions

Answer: (A) Habitat loss and fragmentation

Habitat loss and fragmentation is the most important cause driving animals and plants to extinction.

Q23. Casparian strips present in the endodermis of roots are composed of a waterproof material called:
  1. Chitin
  2. Suberin
  3. Cellulose
  4. Pectin

Answer: (B) Suberin

Casparian strips are waxy bands of suberin deposited on radial and tangential walls of endodermal cells.

Q24. Which of the following is an example of an obligate anaerobe bacterium involved in denitrification?
  1. Rhizobium
  2. Nitrosomonas
  3. Pseudomonas
  4. Azotobacter

Answer: (C) Pseudomonas

Denitrification is carried out by bacteria such as *Pseudomonas* and *Thiobacillus*.

Q25. Which organelle is known as the 'suicide bag' of the cell due to its hydrolytic enzyme content?
  1. Lysosome
  2. Ribosome
  3. Golgi body
  4. Centrosome

Answer: (A) Lysosome

Lysosomes store hydrolytic enzymes capable of digesting cellular components, earning them the name 'suicide bags'.

Q26. The volume of air inspired or expired during normal restful breathing is called:
  1. Inspiratory Reserve Volume (IRV)
  2. Tidal Volume (TV)
  3. Residual Volume (RV)
  4. Expiratory Reserve Volume (ERV)

Answer: (B) Tidal Volume (TV)

Tidal volume is the volume of air inspired or expired during a normal respiration (~500 mL).

Q27. Which cranial nerve in humans is the longest and regulates heart rate and visceral activities?
  1. Trigeminal nerve (V)
  2. Facial nerve (VII)
  3. Vagus nerve (X)
  4. Glossopharyngeal nerve (IX)

Answer: (C) Vagus nerve (X)

Vagus nerve (Cranial nerve X) parasympathetically innervates heart, lungs, and gut.

Q28. In human female reproductive cycle, surge of which hormone triggers ovulation?
  1. FSH
  2. LH
  3. Progesterone
  4. Prolactin

Answer: (B) LH

Rapid secretion of LH leading to maximum level (LH surge) mid-cycle causes rupture of Graafian follicle and release of ovum.

Q29. Which type of immunoglobulin mediates allergic reactions in human body?
  1. IgG
  2. IgM
  3. IgE
  4. IgA

Answer: (C) IgE

IgE antibodies are produced during allergic responses and bind to mast cells, releasing histamine.

Q30. The functional unit of skeletal muscle contraction located between two successive Z-lines is:
  1. Sarcomere
  2. Sarcoplasm
  3. Sarcolemma
  4. Myofibril

Answer: (A) Sarcomere

The portion of myofibril between two successive Z-lines is called a sarcomere, the functional unit of contraction.

Q31. Erythroblastosis fetalis can occur when an Rh-negative mother carries an Rh-positive fetus during:
  1. First pregnancy only
  2. Subsequent Rh-positive pregnancies
  3. Subsequent Rh-negative pregnancies
  4. All pregnancies regardless of Rh factor

Answer: (B) Subsequent Rh-positive pregnancies

Sensitization occurs during 1st delivery; antibodies crossed into fetal circulation in subsequent Rh-positive pregnancies cause erythroblastosis fetalis.

Q32. Gout is a disorder characterized by inflammation of joints due to accumulation of:
  1. Calcium carbonate crystals
  2. Uric acid crystals
  3. Urea crystals
  4. Lactic acid

Answer: (B) Uric acid crystals

Gout is joint inflammation resulting from deposition of monosodium urate / uric acid crystals in joints.