Case Study:

In modern railway systems and high-voltage power transmission networks, engineers must carefully choose the type of metal used for electrical wiring. At first glance, aluminium seems like the better option because it is nearly three times lighter and much cheaper than copper. In fact, many overhead power transmission lines use aluminium cables to reduce overall weight and cost. However, metro trains, underground railway systems, and critical electrical control units still rely heavily on copper wiring.

A railway department conducted a comparison between copper and aluminium wires used in a train control system. It was observed that a copper wire of the same thickness carried electric current more efficiently and produced less heat during continuous operation. Aluminium wires showed higher resistance and expanded more when heated. During testing, engineers also found that aluminium forms a thin oxide layer very quickly when exposed to air. Although this oxide layer protects the metal from further corrosion, it can increase resistance at electrical joints if not maintained properly.

Data from the experiment showed that a copper wire carried 100 units of current with a temperature rise of only 12°C, while aluminium under similar conditions showed a rise of 21°C. In transport systems where signal failure or overheating could become dangerous, even small energy losses matter. Engineers, therefore, select metals not only on the basis of cost, but also by considering conductivity, reactivity, durability, and safety requirements. This decision is closely linked to the reactivity series of metals class 10 and the physical properties of metals studied in NCERT Science. If you find remembering the order a bit tricky, check out this quick reactivity series made simple guide to master it in minutes.

CASE-BASED QUESTIONS

 MCQ 

Q1. Why is copper preferred over aluminium in critical railway control systems?
A. Copper is lighter than aluminium
B. Copper has lower electrical conductivity
C. Copper conducts electricity more efficiently with less heating
D. Copper is more reactive than aluminium

Q2. The oxide layer formed on aluminium mainly:
A. Increases electrical conductivity
B. Prevents further corrosion of aluminium
C. Makes aluminium highly reactive
D. Converts aluminium into a non-metal

 Assertion–Reason 

Q3. Assertion (A): Aluminium is used in many overhead power transmission lines.
Reason (R): Aluminium is lighter and cheaper than copper.
A. Both A and R are true, and R is the correct explanation of A
B. Both A and R are true, but R is not the correct explanation of A
C. A is true, but R is false
D. A is false, but R is true

 Application-Based  

Q4. A metro rail project needs wiring for an underground control room where overheating can become dangerous. Which metal should engineers prefer and why?

Q5. An engineer notices that aluminium joints in a power system require regular maintenance after long use. Using the case study, explain the scientific reason behind this observation.

 Data/Logic-Based 

Q6. In the experiment, copper wires showed a temperature rise of 12°C, while aluminium wires showed 21°C under similar current flow.
What can be concluded from this observation?
A. Aluminium is a better conductor than copper
B. Copper has lower resistance than aluminium
C. Aluminium does not conduct electricity
D. Copper is more reactive than aluminium

 Application + Reasoning  

Q7. Despite being more reactive in the reactivity series class 10, aluminium is still widely used in electrical transmission systems. Give one advantage and one limitation of using aluminium for this purpose.

ANSWER KEY WITH EXPLANATION

A1. C. Copper conducts electricity more efficiently with less heating
Explanation: Copper has lower electrical resistance and better conductivity than aluminium. Therefore, it produces less heat during continuous current flow, making it safer for critical systems.

A2. B. Prevents further corrosion of aluminium
Explanation: Aluminium reacts with oxygen to form a protective oxide layer. This layer prevents further corrosion of the metal but may increase resistance at joints.

A3. A. Both A and R are true, and R is the correct explanation of A
Explanation: Aluminium is widely used in overhead power lines because it is lightweight and economical. These properties make it suitable for long-distance electrical transmission.

A4. Engineers should prefer copper wiring.
Explanation: Copper has higher electrical conductivity and lower heating effect compared to aluminium. This reduces the risk of overheating in underground control systems.

A5. Aluminium forms an oxide layer when exposed to air.
Explanation: The oxide coating increases resistance at electrical joints over time, which can affect performance and require regular maintenance.

A6. B. Copper has lower resistance than aluminium
Explanation: Lower temperature rise means less electrical energy is lost as heat. This indicates that copper has lower resistance and better conductivity.

A7. Advantage: Aluminium is lightweight and cheaper, making it useful for long transmission lines.
Limitation: Aluminium has higher resistance and forms oxide layers that may affect electrical connections.

Struggling to keep all these physical and chemical traits straight? Here is a shortcut on how to remember properties of metals vs non-metals easily before your exams.

 Ready for More Practice 
If you want to ace your upcoming board exams, testing yourself is the best way to build confidence. Dive into these curated resources tailored for Class 10 Chemistry:
Test your timing and exam strategy with a Class 10 Chemistry unsolved practice paper.
Review step-by-step solutions and marking schemes with a Class 10 Chemistry solved practice paper.
Strengthen your core concepts chapter-by-chapter using this targeted Class 10 Chemistry worksheet.

HOTS EXTENSION QUESTIONS

Q1. If scientists develop a new alloy that is as light as aluminium but conducts electricity like copper, how could it change future railway and power systems?

Q2. Predict what may happen if pure iron wires are used instead of copper or aluminium in coastal railway regions. Explain using both conductivity and reactivity concepts.