Electrical Resistance — Prelims Questions

A copper wire of length $L$ and cross-sectional area $A$ has resistance $R$. If the wire is stretched to double its original length, what will be its new resistance?

A conductor has a resistance of $10,Omega$ at $20^circ\text{C}$ and $12,Omega$ at $100^circ\text{C}$. Calculate its temperature coefficient of resistance.

Which of the following materials is generally considered non-Ohmic?

What is the SI unit of resistivity?

Two wires, one of copper and one of nichrome, have the same length and the same cross-sectional area. If the resistivity of nichrome is 50 times that of copper, what is the ratio of the resistance of the nichrome wire to that of the copper wire?

A potential difference of $20,\text{V}$ is applied across a resistor, and a current of $400,\text{mA}$ flows through it. What is the resistance of the resistor?