a2zinterviews

71.	From which minerals is radium obtained?
	A.  Pitchblende
	B.  Limestone
	C.  Haematite
	D.  Rutile

72.	The main constituents of pearl are
	A.  Ammonium sulphate and sodium carbonate
	B.  Calcium oxide and ammonium chloride
	C.  Aragonite and conchiolin
	D.  Calcium carbonate and magnesium carbonate

73.	When a coil is rotated in magnetic field, induced current is generated in the coil. This principle is used in making
	A.  Electric watt meter
	B.  Electric generator
	C.  Electric motor
	D.  Electromagnet

74.	Brass gets discoloured in air because of the presence of which of the following gases in air?
	A.  Oxygen
	B.  Hydrogen sulphide
	C.  Carbon dioxide
	D.  Nitrogen

75.	Which type of fire extinguisher is used for petroleum fire?
	A.  Powder type
	B.  Foam type
	C.  Soda acid type
	D.  None of these