Question

When we stretch a wire, why do we have to do work?

Answer 1

Hint: When we stretch a wire, there is an exertion of force that is responsible for the stretching, then we need to do some work to oppose the force that is exerted while stretching. Ductility is the property which is responsible for the stretching.

Complete answer:
When a wire is stretched, the internal reactive force kicks in and fights the stretch. As a result, work is being done to overcome this opposing force. The wire stores this work in the form of elastic potential energy.
Elastic energy is contained in the bonds that connect atoms in a substance or object. When these linkages are stressed, they collect energy and release it when they relax. Consider it as a coiled spring: when compressed, it absorbs energy and then releases it when it springs back out.
Ductility is a material's physical feature that allows it to be hammered thin or stretched into wire without breaking. A wire can be formed from a ductile substance. Most metals, including gold, silver, copper, erbium, terbium, and samarium, are good examples of ductile materials.
Stretching of wire is possible only due to the ductility property. The ability of a metal to be pulled into wire. When a solid substance stretches under tensile stress, this is known as ductility. A substance can be stretched into a wire if it is ductile.

Note:
When stress is applied, the length of the body lengthens as a result of the force. When a rod is stretched under motion's third law, tensile tension is seen. Tensile stress is commonly seen in rubber. It's the amount of time spent stretching.