If a copper wire is stretched to make its radius decrease by $0.1\%,$ the percentage change in its resistance is approximately.

A cell of emf $E$ having an internal resistance$\mathit{ }r$ is connected to an external resistance $R$. The potential difference $V$ across the resistance $R$ varies with $R$ as shown in figure by the curve :

In a circuit shown in figure resistances $R_1$ and $R_2$are known, as well as emf’s $E_1$ and $E_2$. The internal resistances of the sources are negligible. At what value of the resistance $R$ will the thermal power generated in it be the highest ?

The equivalent resistance between $A$ and $B$ will be (in $\mathrm{\Omega }$)

A wire is in the form of a tetrahedron. The resistance of each edge is $r.$ The equivalent resistances between corners $1–2$ and $1–3$ are respectively-

The equivalent resistance between points $A$ and $B$ is: