A p-n junction diode can be used :

Two charged particles, placed at a distance d apart in vacuum, exert a force F on each other. Now, each of the charges is doubled. To keep the force unchanged, the distance between the charges should be changed to :

A piece of copper and a piece of germanium are cooled from room temperature 20 C down to 80 K. The resistance of

A radioactive sample has a half life of 12 years. The fraction of sample that will decay in 24 years is :

The capacitances of three capacitors are in the ratio 2:3:4. Their equivalent capacitance in parallel combination is more than the equivalent capacitance in series combination by (21/26) pF. The capacitances of the capacitors are, respectively:

Two identical wires X and Y, each of length L carry the same current I. Wire X is bent to form a square of side a and wire Y is bent into a circle of radius R. If \( B_x \) and \( B_y \) are the values of the magnetic field at the centres of the square and the circle respectively, the ratio \( B_x : B_y \) is

The maximum power drawn out of cell is given by : (E is emf, r is internal resistance)

The equation of the plane which passes through the point (3, 2, -1) and is perpendicular to the line with direction ratios 2, 1, 2 is:

Which of the following are correct?
(A) If \(A\) and \(B\) are symmetric matrices such that \(A B=B A\), then \(A B\) is symmetric.
(B) If \(A\) and \(B\) are symmetric matrices of the same order, then \((A+B)\) is a symmetric matrix.
(C) If \(A\) and \(B\) are symmetric matrices of the same order, then \((A B-B A)\) is a symmetric matrix.
(D) If \(A\) and \(B\) are symmetric matrices of the same order, then \((A B+B A)\) is a skew-symmetric matrix.
Choose the correct answer from the options given below :

Read the following paragraph and answer the given questions:
In order to link the alien DNA, the vector needs to have very few, preferably single, recognition sites for the commonly used restriction enzymes. Presence of more than one recognition site in the vector will generate several fragments, which will complicate the gene cloning. In order to link the alien DNA, the vector needs to have very few, preferably single, recognition sites for the commonly used restriction enzymes. Presence of more than one recognition sites within the vector will generate several fragments, which will complicate the gene cloning. The ligation of alien DNA is carried out at a restriction site present in one of the two antibiotic resistance genes. The recombinant plasmids will lose tetracycline resistance due to insertion of foreign DNA but can still be selected out from non-recombinant ones by plating the transformants on tetracycline containing medium.
The recombinants will grow in ampicillin containing medium but not on that containing tetracycline. But, non- recombinants will grow on the medium containing both the antibiotics. In this case, one antibiotic resistance gene helps in selecting the transformants, whereas the other antibiotic resistance gene gets 'inactivated due to insertion' of alien DNA, and helps in selection of recombinants. Origin of replication (ori) is a sequence from where replication starts and any piece of DNA when linked to this sequence can be made to replicate within the host cells. This sequence is also responsible for controlling the copy number of the linked DNA. So, if one wants to recover many copies of the target DNA it should be cloned in a vector whose origin support has high copy number.
Which one of the following is not correct statements about cloning sites of vectors?

Read the following passage carefully and answer the given questions.
During anaerobic sludge digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide. These gases form biogas and can be used as source of energy as it is inflammable. The bioactive molecule, cyclosporin A, that is used as an immunosuppressive agent in organ-transplant patients, is produced by the fungus Trichoderma polysporum. You must have noticed that bottled fruit juices bought from the market are clearer as compared to those made at home. This is because the bottled juices are clarified by the use of pectinases and proteases. Statins produced by the yeast Monascus purpureus have been commercialised as blood-cholesterol lowering agents. It acts by competitively inhibiting the enzyme responsible for synthesis of cholesterol. The BOD test measures the rate of uptake of oxygen by micro-organisms in a sample of water and thus, indirectly, BOD is a measure of the organic matter present in the water.
During anaerobic sludge digestion, bacteria produce the biogas. The composition of this biogas is -

Calculate the molality of KI if the density of 20% (mass/mass) aqueous solution of KI is 1.202 g mL^-1.
(Molar mass of KI is 166 g mol^-1)

Calculate the molality of 25 g of ethanoic acid \(CH(_3\)\(\mathrm{COOH}\)) in 250 g benzene