Q24. Which property is NOT correct for nichrome wire used in electrical heating appliances?
[NCL Assistant Foreman Trainee (Electrical) (4 March 2024, Shift 2)]
(A) It can withstand thermal stress
(B) It has a high temperature coefficient
(C) It has high specific resistance
(D) It has good mechanical strength
Answer: (B) It has a high temperature coefficient
Explanation: Nichrome has high resistivity, withstands elevated operating temperatures and resists oxidation. Its resistance is comparatively stable with changes in temperature, so describing it as having a high temperature coefficient is the incorrect statement. These qualities explain its frequent use in heating appliances.
Q23. What type of mixture is steel?
[Bihar D.El.Ed Official Paper (24 April 2024, Shift 2)]
(A) Alloy
(B) Suspension
(C) Solution
(D) Colloid
Answer: (A) Alloy
Explanation: Steel is an alloy based principally on iron and carbon, with other elements sometimes added to modify its properties. Alloying can improve strength, hardness and corrosion performance. Steel is neither a colloid nor a suspension; in basic general-science classification, it belongs to alloys.
Q22. Which one of the following alloys contains a non-metal as one of its constituents?
[UPSC NDA-II General Ability Test (3 September 2023)]
(A) Brass
(B) Bronze
(C) Amalgam
(D) Steel
Answer: (D) Steel
Explanation: Steel contains iron and carbon, and carbon is a non-metal. Brass combines copper and zinc, while traditional bronze combines copper and tin. Amalgam denotes an alloy involving mercury and another metal. Thus steel is the choice that clearly includes a non-metal constituent.
Q21. Which of the following has the highest resistivity?
[SSC CGL Tier I (17 July 2023, Shift 1)]
(A) Silver
(B) Nichrome
(C) Chromium
(D) Iron
Answer: (B) Nichrome
Explanation: Nichrome is a nickel–chromium-based alloy specially valued for its high resistivity. It converts electrical energy into heat efficiently and tolerates high operating temperatures. Silver is one of the best conductors, while iron and chromium have lower resistivity than typical nichrome heating alloys.
Q20. Which s-block element is used in alloys with copper or nickel for gyroscopes, springs, electrical contacts and non-sparking equipment?
[SSC CHSL Tier I (2 August 2023, Shift 4)]
(A) Beryllium
(B) Rubidium
(C) Francium
(D) Caesium
Answer: (A) Beryllium
Explanation: Beryllium is a lightweight group 2 metal. Small additions to copper produce beryllium-copper alloys with high strength, elasticity and wear resistance. Such alloys are suitable for springs, electrical contacts and non-sparking tools. Rubidium, francium and caesium are much more reactive alkali metals.
Q19. Which of the following metals is always a component of an amalgam?
[SSC MTS 2022-cycle Official Paper (15 June 2023, Shift 1)]
(A) Strontium
(B) Mercury
(C) Zinc
(D) Aluminium
Answer: (B) Mercury
Explanation: An amalgam is an alloy that contains mercury. The other metallic component may vary: examples involve silver, tin, copper and certain other metals. Mercury’s ability to combine with many metals underlies historical applications in dentistry and metallurgy, although mercury exposure presents health risks.
Q18. Duralumin is an alloy made up of aluminium and ________.
[SSC GD Constable 2022-cycle Official Paper (17 January 2023, Shift 4)]
(A) Nickel
(B) Tin
(C) Copper
(D) Zinc
Answer: (C) Copper
Explanation: Duralumin is an aluminium alloy in which copper is an important strengthening constituent. Commercial varieties also include magnesium and manganese. It offers a useful strength-to-weight ratio and was historically important in aircraft structures. It is different from brass, a copper–zinc alloy.
Q17. Which material is preferably used in making heating elements of electrical heating devices?
[RRB Group D (23 August 2022, Shift 1)]
(A) Tin–lead alloy
(B) Nichrome
(C) Tungsten
(D) Constantan
Answer: (B) Nichrome
Explanation: Nichrome combines high electrical resistivity, relatively high operating-temperature capability and good oxidation resistance. These properties allow an electrically powered heating element to produce heat without rapidly deteriorating. Tungsten is more associated with lamp filaments, while constantan is widely used in resistance applications.
Q16. Continuous chips can be produced during machining of which of the following materials?
[MPPSC Assistant Engineer (Mechanical) (3 July 2022)]
(A) Brass
(B) Bronze
(C) Cast iron
(D) Copper
Answer: (D) Copper
Explanation: Copper is highly ductile and can deform plastically into continuous chips during machining under suitable cutting conditions. Cast iron is relatively brittle and usually forms discontinuous chips. Brass and bronze are copper-based alloys, but their machinability and chip formation depend on their particular compositions.
Q15. Solder used for joining metal parts together is an alloy of:
[WBCS Preliminary Examination (22 August 2021)]
(A) Iron and copper
(B) Iron and zinc
(C) Tin and copper
(D) Tin and lead
Answer: (D) Tin and lead
Explanation: Traditional soft solder is made using tin and lead. It melts at a lower temperature than the pieces being joined, enabling a metallurgical connection without melting the base metals. Modern electronics increasingly uses lead-free solders for environmental and health reasons.
