NEET Part Test - 2 - NEET MCQ

Resistance of a conductor is given by R = ρ l/A,
where ρ is the specific resistance, l is the length and A is the cross-sectional area of the conductor.
Now, when l = 1 and A = 1, R = ρ. So specific resistance or resistivity of a material may be defined as the resistance of a specimen of the material having unit length and unit cross-section. Hence, specific resistance is a property of a material and it will increase with the increase of temperature, but will not vary with the dimensions (length, cross section) of the conductor.
 

We want the Voltage difference V_AB.
let A and B be open and not connected to any thing.
There is a current that flows from cell of larger emf to the cell of small emf.
Call that current as  I Amperes.

1.25 V - 0.75 V - I * R2 - I * R1 = 0

I = 0.5 / (R1+R2)
V_AB =  -0.75 - I * R2 =  - 0.75 - 0.5 * R2 / (R1+R2)

= - (0.75 R1 + 1.25 R2) / (R1+R2)

= - ().75 * 1 + 1.25 * 1) / (1 + 1)  volts

=  - 1 volts

60/40 = l/100-l, = R/8

so R=12

now changed position 8 is proportional to l and 12 to (100-l)

8/12 = l/100-l

l = 40ohm

The magnifying power of a telescope tells us how much closer an object appears when viewed through the telescope. If a telescope has a magnifying power of 10, it means the object appears 10 times nearer than it actually is. So, a tree at a certain distance will seem to be at one-tenth of its real distance from the observer.

Magnification of a telescope is given by:
M= θ_i/θ_o​ ​​
10= (h/d_i)/(h/d_o​) ​​
10= d_o​​/d_i​
Distance of image, d_i​=d_o​​/10

This does not mean the tree appears taller; rather, its apparent distance is reduced by a factor of 10, making it appear 10 times nearer.

3/2=v/u…...1
2/3=(v-16)/(u+16)......2
from these equation
we get v=48, u=32
so now f=(vxu)/(v+u)=96/5=19.2
The correct answer is option B.

At infinity, image of B will form at focus since it is at infinity. Image of A will be at A which can be calculated by mirror formula.
1/v​+(1/−u)​=(1/−f)
⟹v= fu /(f−u)​=−( fu/(u−f)​)
Image length = v−f=(fu/(u−f)​)−(f)

= f^2​/(u−f)
(We take the absolute values of the distances to calculate the rod length)

When an object is placed at the centre of curvature then image is formed at radius of curvature. 
So, the minimum distance is zero.
OR
Let focal length be f and an object is placed at u=2f
1/−f=(1/v)+(1/u)=(1/v)+(1/−2f)
v=−2f. 
Image will form at the object location. 
So the minimum distance is zero.

Consider refraction of light from infinity at first surface,
(μ2/v)​​−( μ1/u​)​=(μ2​−μ1/R)​​
(1.5​/ v1​)-(1.75/−∞)​=1.5−1.75​/−R
Consider refraction of this image from second surface,
​(1.75​/ v2)−(​1.5/v1)​=(1.75−1.5​)/R
Hence, v2​=3.5R
This is the image of light coming from infinity, therefore the focal length.
It is converging since focal length is positive.
 

M=−ϑ /u ​=−m/1​
ϑ=−mu
(1/ϑ​)−(1/u)​=1/f
1/mu​+1/u​=−1/f​
(1+m)​/xu=−1/f​
u= (1+m)​f/(m)

To find activity of the sample --->which is the rate of disintegration.

Since radioactivity comes under 1^o kinetics.

[R]=k[A]     [A]-->amount of initial sample 10¹⁸ atoms

Given,

Half-life=2days

K=0.693/2x24x60x60 sec

R=(0.693/2x24x60x60)x10¹⁸

R≈3.5x10¹² Bq

aul Ehrlich, a Stanford ecologist gave the ‘Rivet popper hypothesis’. In this hypothesis, he considered species as a rivet. This hypothesis provides a perspective on what might happen if a few species of the planet are extinct.

Keystone species are those which have significant and disproportionately large influence on the community structure and characteristics. It has often considerably low abundance and biomass as compared to dominant species. Removal of such species causes serious disruption in structure and function of community.

A. Beta diversity - Between community diversity
B. Rich biodiversity - Tropical areas
C. Gamma diversity - Diversity of whole geographical region
D. Extinct species - Dodo
E. Critically endangered species - Great Indian bustard

When the biomass of producer is less and that of the consumer is more the pyramid will have an inverted shape. It occurs in a pond and lake ecosystem. Here the biomass of diatoms in planktons is negligible as compared to their date of crustaceans and small fishes. inverted pyramid soil found in that ecosystem where the number and biomass of producers of more and those of consumers are less.
In most of the ecosystems, the number of the biomass of producers is more than those of a consumer is less. This type of ecosystem has a pyramid where the apex is pointed upwards. This type of pyramid is known as upright pyramid.
In some ecosystem, the number of the producers is more than the consumers. The apex is pointed upwards. This is known as the upright pyramid of the number. Found in the grassland ecosystem.

In competition, both species are harmed. In predation and parasitism, one species derives benefit and the other one is harmed. Commensalism is an interaction in which one species is benefitted and other one remains unaffected.

Topic in NCERT: Population Interactions

Line in NCERT: "Even in minimal communities, many interactive linkages exist, although all may not be readily apparent. Interspecific interactions arise from the interaction of populations of two different species. They could be beneficial, detrimental or neutral (neither harm nor benefit) to one of the species or both."

An example of microbial biocontrol agent is bacteria Bacillus thuringiensis (Bt).
It can be introduced in order to control butterfly caterpillars.
These are available in sachets as dried spores that are mixed with water and sprayed onto vulnerable plants such as Brassica and fruit trees, where these are eaten by the insect larvae. In the gut of larvae, the toxin is released and the larvae get killed. The bacterial disease will kill the caterpillars, but leaves other insect uharmed. 

Trichoderma polysporum is a fungal species that is known to make cyclosporine A compound. This compound exhibits antifungal and anti-inhibitory properties. The key property of this compound is that it is able to inhibit the activation of T-cells. These cells are involved in recognizing foreign and self elements. During the time of grafting usually, our body rejects the graft as T-cells recognize it as foreign. But using cyclosporine A we can inhibit this rejection by T-cells. So, the medical application of Cyclosporin A is an immunosuppressive agent.
Monascus purpureus is a yeast strain belonging to the fungus that is known to make statin. Statin is a competitive inhibitor of cholesterol synthesis. This means that it negatively affects the cholesterol synthesis process. So, its medical application is that it is used to lower blood cholesterol levels.
Thus, from the above discussion, we can conclude that option A is the correct answer.

The primary purpose of passing effluent into a settling tank is to allow bacterial flocs to sediment, which helps in further purification of the sewage.

Reverse transcription takes place during the formation of viral genomic RNA from DNA.

Elephantiasis or filariasis is caused by a number of worms. However, in India only two types of worms are responsible for this disease, Wuchereria bancrofti and W. malayi.This disease is transmitted by female Cu/exmosquitoes. Elephantiasis affects lymphatic vessels of the lower limbs.

• Typhoid - Salmonella typhi
• Pneumonia - Streptococcus pneumoniae
• Malaria - Plasmodium
• Ringworm - Trichophyton

When a female Anopheles mosquito bites an infected person, Plasmodium enters the mosquito's body and undergoes further development. The parasites multiply within them to form sporozoites that are stored in their salivary glands.

There are no side effects of tubectomy and vasectomy. Purpose of tubectomy is to prevent egg transport.
Contraceptive pills help in birth control by preventing ovulation. Genital warts is a sexually transmitted disease caused by human papilloma virus (HPV). In India, there is rapid decline in - IMR and MMR due to better health facilities.

Topic in NCERT: Contraceptive methods and reproductive health

Line in NCERT: "Sterilisation procedure in the male is called 'vasectomy' and that in the female, 'tubectomy'. In vasectomy, a small part of the vas deferens is removed or tied up through a small incision on the scrotum whereas in tubectomy, a small part of the fallopian tube is removed or tied up through a small incision in the abdomen or through vagina. These techniques are highly effective but their reversibility is very poor."

Small doses of either progestogens or progesterone-estrogen combinations are used in the form of tablets by females called oral pills. Pills inhibit ovulation and implantation as well as alter the quality of cervical mucus to prevent or retard entry of sperms inside female genital tract.

In the given figure: 
A. Seminal vesicle
B. Vas deferens
C. Prostate gland
D. Bulbourethral gland
E. Urethra
F. Epididymis
G. Seminiferous tubules

Given figure represents an anatropous ovule.

(i) Diploblastic - Poriferans, Coelenterates

(ii) Triploblastic - Platyhelminthes to Chordates

(iii) Acoelomate - Poriferans, Coelenterates, Platyhelminthes

(iv) Pseudocoelomate - Aschelminthes/Roundworms

(v) Eucoelomate - Annelids to Chordates

So, the correct answer is '(i), (ii), (iii), (iv) and (v)'.

Line in NCERT: "Animals in which the cells are arranged in two embryonic layers, an external ectoderm and an internal endoderm, are called diploblastic animals, e.g., coelenterates. Those animals in which the developing embryo has a third germinal layer, mesoderm, in between the ectoderm and endoderm, are called triploblastic animals (platyhelminthes to chordates)."

Flagellated protozoans: The members of this group are either free-living or parasitic. They have flagella. The parasitic forms cause diaseases such as sleeping sickness. Example: Trypanosoma

Line in NCERT: "Flagellated protozoans: The members of this group are either free-living or parasitic. They have flagella. The parasitic forms cause diseases such as sleeping sickness. Example: Trypanosoma."