Engineering :: Renewable Sources of Energy

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81.

p-type silicon is formed by adding a minute amounts of elements with

A.	three valence electrons	B.	four valence electrons
C.	five valence electrons	D.	six valence electrons

82.

At room remperature the theoretical maximum efficiency of a perfect solar cell cannot exceed about

A.	2%	B.	45%
C.	99%	D.	5%

83.

One eV is defined as the energy gained by an electron when it is accelerated by a voltage difference of

A.	1 V	B.	1 kV
C.	1 MV	D.	1 mV

84.

The energy content of a photon corresponding to waves in the blue wavelength region is

A.	more than that for waves in red portion of the spectrum	B.	less than that for waves in red portion of the spectrum
C.	equal to that for waves in red portion of the spectrum	D.	none of the above

85.

Suppose that hot water is stored at a temperature that is 25?C higher than room temperature. Water required to store 1 million cal of heat is about

A.	40 litre	B.	40 kilolitre
C.	25 litre	D.	2500 litre

86.

If the thickness of insulation in the walls and ceiling of a house is doubled the heat loss is expected to decrease by a factor of

A.	none	B.	2
C.	4	D.	16

87.

For a 25?C rise in temperature which of the following maerials will store the most heat?

A.	A ton of water	B.	A ton of iron
C.	A ton of rocks	D.	A ton of wood

88.

In USA the mixture of 26.5% diphenyl and 73.5% diphenyl oxide is known as

A.	Dowtherm G	B.	Dowtherm J
C.	Dowtherm A	D.	Dowtherm HT

89.

Pour point of a fluid

A.	relates to a considerable increase of viscosity with decrease in temperature	B.	refers to the change of phase from liquid to solid
C.	refers to sudden discontinuity in fluid properties	D.	none of the above

90.

Which of the following is maximum for aniline?

A.	Flash point	B.	Fire point
C.	Ignition point	D.	Boiling point