Solder is an alloy of
- (a)Cu and Sn.
- (b)Fe and Zn.
- (c)Pb and Sn.
- (d)Ag and Zn.
Correct — C, Pb and Sn. Solder is an alloy of lead (Pb) and tin (Sn) — typically around 60 per cent tin with the rest lead — valued for its low melting point, which lets it join metal parts and electrical components without melting them. The other pairs are different materials: Cu-Sn is bronze, Fe-Zn is galvanised (zinc-coated) iron, and Ag-Zn is a battery couple.
- (a)Cu and Sn. — Copper and tin make bronze, not solder.
- (b)Fe and Zn. — Iron coated with zinc is galvanised iron; this is not a solder alloy.
- (d)Ag and Zn. — Silver and zinc are used in some cells and batteries, not as ordinary solder.
Solder is a fusible metal alloy — classically tin and lead — used to join two metal surfaces, especially in electronics and plumbing. Its key property is a low melting point, well below that of the metals being joined.
Remember 'solder = soft, low-melting = tin plus lead'. Each distractor is a different well-known alloy or couple, so recognising bronze and galvanised iron lets you eliminate them.
- Solder is an alloy of tin (Sn) and lead (Pb) with a low melting point.
- A common composition is about 60 per cent tin and 40 per cent lead (eutectic near 63/37).
- Bronze is copper and tin; galvanising is a zinc coating on iron or steel.
- Lead-free solders, such as tin-silver-copper, are now common for health and environmental reasons.
- Confusing solder (Pb-Sn) with bronze (Cu-Sn).
- Mixing up galvanising (zinc on iron) with a solder alloy.
Asked as 'solder is an alloy of...' among other named alloys — recall the tin-lead pair.
UPSC_2006_GS1_Q1282006Which are the materials generally employed as solder in soldering operation in electronics?
- (a) Iron and tin
- (b) Lead and tin
- (c) Aluminum and lead
- (d) Aluminum and iron
Answer(b) Lead and tin
Same fact — the composition of solder. That UPSC item asks which materials are used as solder in electronics (lead and tin); this NDA item states the same tin-lead alloy.
- practice — not a real PYQ
Bronze is an alloy of
- (a)copper and tin
- (b)copper and zinc
- (c)lead and tin
- (d)iron and carbon
Answer(a) copper and tin.
- practice — not a real PYQ
The property that makes tin-lead solder useful for joining components is its
- (a)high melting point
- (b)low melting point
- (c)magnetism
- (d)transparency
Answer(b) low melting point.