The net emf and internal resistance of three batteries as shown in figure is 

    

A conducting solid sphere is joined in an electrical circuit as shown in figure. Two imaginary points $A$ and $B$ are taken inside the sphere. For given conditions

In the diagram shown, all the wires have resistance $R$. The equivalent resistance between the upper and lower dots shown in the diagram is

An electric bell has a resistance of $5\Omega$ and requires a current of $0.25 A$ to work it. Assuming that the resistance of the bell wire is $1\Omega$ per $15 \mathrm{m}$ and that the bell push is $90 \mathrm{m}$ distance from the bell. How many cells each of emf $1.4 \mathrm{V}$ and internal resistance $2\Omega$, will be required to work the circuit

A wire has resistance of $24 \mathrm{\Omega }$ is bent in the following shape. The effective resistance between $A$ and $B$ is