Three charges, +Q, q and +Q are placed with q at mid point of the line joining the other two charges. For the system of charges to be in equilibrium, the value of q is

A radioactive source (Phosphorus-32) has an initial activity 10 \(\mu\)Ci, its half life is 14 days. What time elapses before the activity falls to 1.25 \(\mu\)Ci ?

A pure silicon crystal has \( 5 \times 10^{28} \text{ atoms m}^{-3} \). It is doped by 2 ppm concentration of pentavalent arsenic. The number of holes are: (Consider \( n_i = 1.5 \times 10^{16} \text{ m}^{-3} \))

A current of \( 2 \times 10^{-5} \text{ A} \) produces 25 division deflection in a galvanometer. The resistance of the galvanometer coil is \( 4 \ \Omega \). The figure of merit of galvanometer is :

A convex lens of focal length 20 cm and two concave lenses of focal length 10 cm and 30 cm are placed in contact with each other. The focal length of the combined three lenses will be.

A square coil of side 10 cm, 500 turns and resistance 3 \(\Omega\) is placed with its plane perpendicular to the horizontal component of the Earth's magnetic field. It is rotated about vertical axis passing through centre by 180° in 0.25 second. Estimate the magnitude of the emf and current induced in the coil. Horizontal component of the Earth's magnetic field at the place is 3.0 \(\times 10^{-5}\) T.

A current of 2 A flows through a plane circular coil of radius 3 cm and having 50 turns. The coil has been placed in a uniform magnetic field of 0.6 T. The minimum potential energy of the coil will be

Which one of the following is not true for a molecule that can act as a genetic material?

A solenoid with \(2 \times 10^4\) turns per meter, diameter 0.1 m , has a coil of 100 turns and 0.01 m radius placed inside. If solenoid current decreases from 4 A to 0 in 0.05 s , total charge through coil is :

We use microbes and microbially derived products almost every day. Bacteria called lactic acid bacteria (LAB) grow in milk to convert it into curd. The dough, which is used to make bread, is fermented by yeast called Saccharomyces cerevisiae. Microbes are used to produce industrial products like lactic acid, acetic acid and alcohol, which are used in a variety of processes in the industry. However, certain bacteria, which grow anaerobically on cellulosic material, produce large amount of methane along with CO2 and H2. These bacteria are collectively called methanogens, and one such common bacterium is Methanobacterium. These bacteria are commonly found in the anaerobic sludge during sewage treatment. Microbes are also used for commercial and industrial production of certain chemicals like organic acids, alcohols and enzymes.
Examples of acid producers are Aspergillus niger (a fungus) of citric acid. You are familiar with the commonly used antibiotic Penicillin. Do you know that Penicillin was the first antibiotic to be discovered, and it was a chance discovery? 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 discovery of penicillin was a chance discovery by Alexander Fleming while working on:

Identify the essential amino acids from the following.
(A) Threonine
(B) Serine
(C) Histidine
(D) Lysine
Choose the correct answer from the options given below :

Which among the following metals shows 6 secondary valencies ?
(A) 1 mole of \(PdCl _2 \cdot 4 NH _3\) reacts with excess of \(AgNO _3\) to give 2 moles of AgCl precipitated
(B) 1 mole of \(NiCl _2 \cdot 6 H _2 O\) reacts with excess of \(AgNO _3\) to give 2 moles of AgCl precipitated
(C) 1 mole of \(PtCl _4 \cdot 2 HCl\) does not give reaction with \(AgNO _3\)
(D) 1 mole of \(CoCl _3 \cdot 4 NH _3\) reacts with excess of \(AgNO _3\) to give 1 mole of AgCl precipitated
(E) 1 mole of \(PtCl _2 \cdot 2 NH _3\) does not give reaction with \(AgNO _3\)
Choose the correct answer from the options given below :

The chromosomal disorders are caused due to absence, excess or abnormal arrangement of one or more chromosomes. Failure of segregation of chromatids during cell division results in the gain or loss of chromosome(s), called aneuploidy.
Which of the following statements are correct with respect to the humans suffering from the disorder?
(A) One in every 800 live births shows this karyotype
(B) The affected individual has 45 chromosomes.
(C) Non-disjunction of chromosomes at the time of gamete formation causes this disorder.
(D) In this disorder, individual has 45 autosomes
Choose the correct answer from the options given below: