In electrical work, the common soft solder used by electricians typically has which approximate composition by mass?

Introduction / Context:
Electricians often use soft solder to join copper wires and electronic components. This solder is usually an alloy of lead and tin chosen for its relatively low melting point and good wetting properties. Knowing the typical composition of electrician solder is useful in basic electronics and trade related general knowledge. This question asks you to identify the approximate lead tin ratio used in common soft solder.

Given Data / Assumptions:

• Soft solder is usually a lead tin alloy.
• A common formulation for electrical work is close to the eutectic composition of the lead tin system.
• The eutectic composition has a low, sharp melting point, desirable for soldering.
• The options list different combinations of metals and percentages.

Concept / Approach:
The classic soft solder for electronics and electrical joints is an alloy of about 63% tin and 37% lead by mass. This composition is close to the eutectic point, where the alloy melts at a single relatively low temperature and solidifies quickly, which is ideal for making clean, reliable joints. Alloys including iron or steel are not used as soft solder because they have much higher melting points and poor wetting characteristics on copper conductors. Therefore, the correct option is the one that lists lead 37% and tin 63%.

Step-by-Step Solution:
Step 1: Recall that traditional soft solder used in electronics is a lead tin alloy.Step 2: Remember that the eutectic composition of lead tin solder is approximately 63% tin and 37% lead.Step 3: Recognise that eutectic solder melts and solidifies at a single temperature, making it easier to use.Step 4: Examine the options for a composition that matches lead 37% and tin 63%.Step 5: Notice that other options mention iron, steel or copper instead of the correct lead tin combination.Step 6: Conclude that lead 37% and tin 63% is the correct electrician solder composition.

Verification / Alternative check:
Datasheets and electronics textbooks refer to common solders by numbers such as 60 40 or 63 37, where the first number is the tin percentage. The alloy labelled 63 37 is described as eutectic with a melting point around 183 degrees Celsius. This formulation has been widely used for many years in electronic assembly and electrical joints, confirming that the given percentages are realistic and widely accepted.

Why Other Options Are Wrong:
Iron 37% and tin 63% would have a much higher melting point and is not used as a soft solder in electrical work. Lead 37% and steel 63% is unrealistic because steel is itself an alloy and has poor soldering characteristics for copper conductors. Steel 37% and copper 63% would not form a standard soft solder alloy and would require very high temperatures, completely unsuitable for normal electrical soldering.

Common Pitfalls:
Students may mistakenly assume that any mixture with tin will work as solder or may not pay attention to the percentages. Others may confuse hard solder (brazing alloys) containing copper or silver with soft solder. To avoid such confusion, remember that traditional soft electrician solder is a lead tin alloy near 63% tin and 37% lead by mass.

Final Answer:
Common electrician soft solder typically contains about 37% lead and 63% tin by mass.