On heating n-type semiconductors -

Two parallel conductors each carrying a current of 10 mA in opposite directions are placed at a distance 10 cm apart. The force per unit length between two conductors is

Eight cells each having emf 2 V and internal resistance \( r = 0.02 \Omega \) are connected in series with an external resistance 9 \( \Omega \). The current flowing through the external resistance (I) is

Two identical metal balls, A and B, with similar charges Q are suspended with insulating threads. They repel each other with a force F. Another identical uncharged metal ball C is first touched with metal ball A and then touched with metal ball B and finally removed. The new force of repulsion between A and B will be

A Wheatstone bridge has four resistors: R1= R2 = R3 = 1 \( \Omega \) and R4 = 2 \( \Omega \). In order to balance the bridge, resistor R4 has to be shunted by resistance of

Read the following statements regarding energy levels, and identify the correct statements.
(A) The energy of an atom is least when its electron is revolving in an orbit closest to the nucleus
(B) the energy levels of the excited states come closer and closer together as principal quantum number increases
(C) ionisation energy of the hydrogen atom is the minimum energy required to free the electron from the ground state of the hydrogen atom
(D) as the excitation of hydrogen atom increases, the value of minimum energy required to free the electron from the excited atom decreases.
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The resistivity of a wire depends on :
(A) its length
(B) its area of cross-section
(C) its temperature
(D) nature of material
(E) voltage applied across it
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The cutting of DNA at specific locations is done with help of:

Detritus food chain begins with :

Match List I with List II

List I (Terms)	List ll (Features)
(A) Natality	(I) Exit of individuals
(B) Mortality	(II) Entry of individuals
(C) Immigration	(III) Death rate
(D) Emigration	(IV) Birth rate

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Arrange the following steps of sewage treatment in a sequential order.
(A) Primary effluent passed in aeration tank
(B) Activated sludge is formed
(C) Filtration and sedimentation of sewage
(D) Aerobic microbes grow into flocs
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Which disease is not the sexually transmitted infection?

Arrange the following events of Meselson and Stahl's experiment in order of their occurence:
A. DNA extracted from the culture, twenty minutes after transfer from 15N to 14N medium had a hybrid density.
B. E. Coli with heavy DNA were transferred into a medium with 14NH4CI. Coli were grown in a medium containing 15NH4CI.
C. E.
D. DNA extracted from the culture after forty minutes had equal amounts of hybrid DNA and light DNA.
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