Physics-2000-Set-I

Q1) Give a reason to show that microwaves are better carriers of signals for long range transmission than radio waves. (Marks 1)
Ans1) Microwaves have smaller wavelength due to which they can be transmitted as beam signals in a particular direction, better than radiowaves because microwaves do not spread or bend around the corners of any obstacle coming in their way.

Q2) How does the energy gap in an intrinsic semiconductor vary, when doped with a pentavalent impurity ? (Marks 1)
Ans2) The energy energy gap in semiconductor decreases when doped with a petavalent impurity.

Q3) State the condition in which terminal voltage across a secondary cell is equal to its e.m.f (Marks 1)
Ans3) The terminal voltage across a secondary cell is equal to its e.m.f. when no current is drawn from it i.e., it is in an open circuit.

Q4) Draw an equipotential surface in a uniform electric field.
(Marks 1)

Ans4)
(Equipotential surfaces are parallel planes at 90o to field lines)

Q5) If the number of turns of a solenoid is doubled, keeping the other factors constant, how does the self-inductance of the solenoid change ? (Marks 1)
Ans5) The self inductance becomes four times on doubling the no of turns of solenoid since L = oN2A/e , L N2

Q6) What is the ration of solar constants on the surfaces of two planets, whose surface temperatures are in the ratio 1 :2 ? (Marks 1)
Ans6) Solar constant (Temp)4
S1/S2 = (T1/T2)4 = (1/2)4 = !/16
or S1 : S2 = 1 : 16

Q7) The wavelength of light coming from a distant galaxy is red-shifted. Is the galaxy receding or approaching the earth ? (Marks 1)
Ans7) The red shift indicates that the galaxy is receding

Q8) What is the angle of dip at a place where the horizontal and vertical components of earth’s magnetic field are equal ? (Marks 1)
Ans8) tan = BV/BH = 1
= 45o

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