Explore topic-wise InterviewSolutions in Current Affairs.

It is a thermodynamic process which occurs at a constant pressure.

Statement: If two bodies A and B are in thermal equilibrium and also A and C are in thermal equilibrium then B and C are also in thermal equilibrium.

Explanation:

1. Consider two sections of a container separated by an adiabatic wall containing two different gases as system A and system B.

2. Systems A and B are independently brought in thermal equilibrium with a system C.

3. When the adiabatic wall separating systems A and B is removed, there will be no transfer of heat from system A to system B or vice versa.

4. This indicates that systems A and B are also in thermal equilibrium.

5. This means, if systems A and B are separately in thermal equilibrium with a system C, then A and B are also mutually in thermal equilibrium.

The limitations of the first law of thermodynamics are

(i) It does not give the direction of flow of heat.

(ii) It does not explain why all heat cannot be converted into work.

Correct answer is (b) Wood

(d) North – South

i) After some time it becomes stationary.

ii) I found that the magnet rests in a north-south direction. You will notice that the magnet finally takes a position in the North-South direction. Mark the endpoints towards the North with some color. Now disturb the magnet and again wait for some time.

iii) The colored portion comes to rest towards the north.

iv) I observed that the magnets always come to rest in the North-South direction.

Correct option is: (A) JK^-1 mole^-1

(i) Objectives :

To understand the need to have temporary and permanent magnets.

To understand the need to use different materials for making magnets. 

(ii) Uses of Electromagnets :

Used in electric bells, loudspeakers, electric motors, telephone diaphragms, electric fan and for sorting scrap metal and for extraction in hospitals, etc.

(B) (a)-(iii), (b)-(iv), (c)-(i), (d)-(ii) 

(D) Electricity produced is not cheap. 

Correct option (D) All of these.

Explanation:

Wave power project requires minimum land area.

(D) Wave power project requires large land area,

(D) All of these.

We would use a microwave oven for heating the food as it heats uniformly and clearly without any loss in its nutritional value.

A good source of energy is
(i) one which would do a large amount of work per unit volume or mass.
(ii) which is easily accessible.
(iii) which is easy to store and transport; and
(iv) perhaps most importantly, economical.

(a) The values shown by the science students are :

(i) high degree of general awareness, and

(ii) sense of responsibility.

(b) Photocell.

(c) A person approaching a doorway may interrupt a light beam which is incident on a photocell. The abrupt change in photo-current records every interruption of the light beam caused by the person passing across the beam. In this way it helps count the person entering the auditorium, provided they enter the hall one by one.

In the first case man applies an upward force of 25 kg weight.

Hence the action on the floor by man is

= 50 kg weight + 25 kg weight = 75 kg weight

= 75 × 10

= 750 N.

In the second case man applies a downward force of 25 kg

weight. Hence the action on the floor by man is

= 50 kg weight – 25 kg weight = 25 × 10

= 250 N. 

(Other 500 N is applied on the ceiling) Hence man should adopt the second case.

750 N and 250 N in the respective cases; Method (b)
Mass of the block, m = 25 kg
Mass of the man, M = 50 kg
Acceleration due to gravity, g = 10 m/s² 

Force applied on the block, F = 25 × 10 = 250 N
Weight of the man, W = 50 × 10 = 500 N
Case (a): When the man lifts the block directly 

In this case, the man applies a force in the upward direction. This increases his apparent weight.

Action on the floor by the man = 250 + 500 = 750 N
Case (b): When the man lifts the block using a pulley
In this case, the man applies a force in the downward direction. This decreases his apparent weight.

Action on the floor by the man = 500 – 250 = 250 N
If the floor can yield to a normal force of 700 N, then the man should adopt the second method to easily lift the block by applying lesser force.

750 N and 250 N in the respective cases; Method (b)

Mass of the block, m = 25 kg 

Mass of the man, M = 50 kg 

Acceleration due to gravity, g = 10 m/s² 

Force applied on the block, F = 25 × 10 = 250 N 

Weight of the man, W = 50 × 10 = 500 N 

Case (a): When the man lifts the block directly

In this case, the man applies a force in the upward direction. This increases his apparent weight.

Action on the floor by the man = 250 + 500 = 750 N

Case (b): When the man lifts the block using a pulley 

In this case, the man applies a force in the downward direction. This decreases his apparent weight.

Action on the floor by the man = 500 – 250 = 250 N

If the floor can yield to a normal force of 700 N, then the man should adopt the second method to easily lift the block by applying lesser force.

In the mode (a), Figure. shown the man applies an upward force of 25 kg wt. (same as weight of the block).

According to Newton's third law of motion, there will be a downward reaction on the floor.

The action on the floor by man = 50 kg wt + 25 kg wt = 75 kg wt

= 75 x 10 N = 750 N

In mode (b), the man applies an upward force of 25 kg wt. (same as the weight of the block). According to Newton's third law of motion, the reaction is in the upward direction.

In this case, action on the floor by the man

= 50 kg wt - 25 kg wt = 25 kg wt

= (25 x 10) N = 250 N

Mode (b) should be adopted

(i) The centripetal force is provided by the lateral force acting due to rails on the wheels of the train.

(ii) The outer rails wear out faster

(iii) tanθ = v²/rg ⇒ tanθ = {(15)²}/{30 x 9.8} = 0.7653 = tan 37.4°

θ = 37.4° = 37° 25'

Here tanθ = v²/rg

⇒ r = {v²}/{g tanθ} = {(200)²}/{9.8 x tan 15°}

or r = 15232 m = 15.23 km

C) Newton’s Third law

a) Force on the seventh coin is exerted by the weight of the three coins on its top.

Weight of one coin = mg

Weight of three coins = 3mg

Hence, the force exerted on the 7^th coin by the three coins on its top is 3mg. This force acts vertically downward.

b) Force on the seventh coin by the eighth coin is because of the weight of the eighth coin and the other two coins (ninth and tenth) on its top.

Weight of the eighth coin = mg 

Weight of the ninth coin = mg 

Weight of the tenth coin = mg 

Total weight of these three coins = 3mg

Hence, the force exerted on the 7^th coin by the eighth coin is 3mg. This force acts vertically downward.

c) The 6^th coin experiences a downward force because of the weight of the four coins (7^th , 8^th, 9^th, and 10^th) on its top. 

Therefore, the total downward force experienced by the 6^th coin is 4mg. 

As per Newton’s third law of motion, the 6^th coin will produce an equal reaction force on the 7^th coin, but in the opposite direction. Hence, the reaction force of the 6th coin on the 7^th coin is of magnitude 4mg. This force acts in the upward direction.

(a) The force on 7^th coin is due to weight of the three coins lying above it. 

Therefore, F = (3 m) kgf = (3 mg) N 

Where g is acceleration due to gravity. This force acts vertically downwards. 

(b) The eighth coin is already under the weight of two coins above it and it has its own weight too. Hence force on 7th coin due to 8th coin is sum of the two forces i.e. 

 F = 2m + m = (3m) kg f = (3 mg) N

The force acts vertically downwards. 

(c) The sixth coins is under the weight of four coins above it 

Reaction, R = -F = -4 m (kgf) = - (4 mg) N

-ve sign indicates that reaction acts vertically upwards.

The force of friction will be present only as long as there is relative motion between the two bodies and it automatically disappears as soon as the relative motion ceases.

When the thief is in air, he is in the state of free fall, and hence in the state of weightlessness. So, the force of the load on his back is zero.

When the thief is in the air, he is falling freely and hence in the state of weightlessness. Therefore the force of the load on his back is zero.

Weight of the box W = m (g – a) = m (g – g) = 0. 

The process by which a gene's coded information is converted into the structures present and operating in the cell. Expressed genes include those that are transcribed into mRNA and then translated into protein and those that are transcribed into RNA but not translated into protein (eg. transfer and ribosomal RNAs).

Determination of the relative positions of genes on a DNA molecule (chromosome or plasmid) and of the distance, in linkage units or physical units, between them. 

Credit card or Debit card or ATM machine or Swipe machine 

Cyberspace is a virtual environment created by computer systems connected to the internet

The fundamental physical and functional unit of heredity. A gene is an ordered sequence of nucleotides located in a particular position on a particular chromosome that encodes a specific functional product (i.e., a protein or RNA molecule)

PCR reaction is a DNA synthesis reaction that depends on the extension of primers annealed to opposite strands of a dsDNA template that has been denatured (melted apart) at temperatures near boiling. By repeating the melting, annealing and extension steps, several copies of the original template DNA can be generated.

The amount of starting material (target) needed is very small. 

Not necessary to isolate the desired sequence, because it will be defined by the primers that are used in the reaction. The primers are oligonucleotides complementary to different regions on the 2 strands of DNA template (flanking the region to be amplified). 

The primer acts as a starting point for DNA synthesis. The oligo is extended from its 3' end by DNA polymerase. 

Critical evidence of a particular crime is available in electronic format with the help of computer forensics. It helps to identify the criminal.

A Physical mapping approach that uses fluorescein tags to detect hybridization of probes with metaphase chromosomes and with the less-condensed somatic interphase chromatin. 

Study of genes, their resulting proteins, the role played by proteins in the body's biochemical processes.

PCR is a technique for the in vitroamplification of a desired sequence of DNA. PCR allows the generation of a large quantity of DNA product (up to several g) from only a few starting copies. It has been shown that PCR can be used to generate a detectable quantity of DNA from only one starting target (or template) molecule. 

PCR developed in the mid-1980's, has found multiple applications, such as: 

1. Rapid amplification of intact genes or gene fragments 

2. Generation of large amounts of DNA for sequencing 

3. Generation of probes specific for uncloned genes by selective amplification of a specific segment of cDNA 

4. Analysis of mutations for medical applications 

5. Detection of minute amounts of DNA for forensic purposes 

6. Amplification of chromosomal regions adjacent to genes of known sequence and many more·

Use of DNA for identification. Some examples of DNA use are to establish paternity in child support cases; establish the presence of a suspect at a crime scene, and identify accident victims. 

(a) Sequencing :

Determination of order of nucleotides (base sequences) in a DNA or RNA molecule or the order of amino acids in a protein. The X or Y chromosome in human beings that determines the sex of an individual. Females have two X chromosomes in diploid cells; males have an X and a Y chromosome. The sex chromosomes comprise the 23rd chromosome pair in a karyotype. 

(b) Shotgun method :

Sequencing method that involves randomly sequenced cloned pieces of the genome, with no foreknowledge of where the piece originally came from. This can be contrasted with "directed" strategies, in which pieces of DNA from known chromosomal locations are sequenced. Because there are advantages to both strategies, researchers use both random (or shotgun) and directed strategies in combination to sequence the human genome.

Applications of PCR :

(1) Cloning a gene encoding a known protein 

(2) Amplifying 'old DNA' 

(3) Amplifying cloned DNA from vectors 

(4) Creating mutations in cloned genes 

(5) Rapid amplification of cDNA ends - RACE 

(6) Detecting bacterial or viral infection 

• AIDs infection
• Tuberculosis (Mycobacterium tuberculosis) 

(7) Cancer Detecting mutations that occur in cancer and monitoring cancer therapy. Determining if a patient is free of malignant cells 

(8) Genetic diagnosis 

a. Diagnosing inherited disorders 

b. Diagnosing cancer 

c. Blood group typing

d. Prenatal diagnosis

A vector that can replicate in the cells of more than one organism (e.g. YAC vector in E.coli and in yeast). 

The breaking during meiosis of one maternal and one paternal chromosome, the exchange of corresponding sections of DNA, and the rejoining of the chromosomes. This process can result in an exchange of alleles between chromosomes. See also:recombination

A segment of double-stranded DNA in which the nucleotide sequence of one strand reads same in reverse order to that of the complementary strand. 

DNA sequence variations that occur when a single nucleotide (A, T, C, or G) in the genome sequence is altered.