Lamps used for household lighting are connected in

In an aluminium $(Al)$ bar of square cross-section,a square hole is drilled and is filled with iron $(Fe)$ as shown in the figure. The electrical resistivities of $Al$ and $Fe$ are $2.7 \times 10^{-8} \ \Omega m$ and $1.0 \times 10^{-7} \ \Omega m$,respectively. The electrical resistance between the two faces $P$ and $Q$ of the composite bar is

For the shown circuit,find the effective resistance between the points $A$ and $B$.

When a wire of uniform cross-section $a$,length $ℓ$,and resistance $R$ is bent into a complete circle,the resistance between any two diametrically opposite points will be .......

Two heater wires of equal length are first connected in series and then in parallel. The ratio of heat produced in the two cases is

What is meant by parallel connection of resistors? Derive the equation for equivalent resistance in a parallel circuit.