If $400\; \Omega$ of resistance is made by adding four $100\; \Omega$ resistors of tolerance $5\%$ each,then the tolerance of the combination is .....$\%$

$A$ wire with a resistance of $0.5 \, \Omega \, m^{-1}$ is bent into a circle of radius $1 \, m$. $A$ similar wire is connected across its diameter. What is the equivalent resistance between the two ends of the diameter?

$A$ heating coil can heat the water of a vessel from $20\,^oC$ to $60\,^oC$ in $30$ minutes. Two such heating coils are put in series and then used to heat the same amount of water through the same temperature range. The time taken now will be ............ $min$ (neglecting thermal capacity of the coils).

$A$ straight wire of resistance $18 \Omega$ is bent in the form of an equilateral triangular loop. The effective resistance between any two vertices of the triangle is (in $Omega$)

$A$ technician has only two resistance coils. By using them singly, in series or in parallel, he is able to obtain the resistances $3, 4, 12$ and $16 \, \Omega$. The resistances of the two coils are ........... $\Omega$.

$A$ wire of resistance $12 \,\Omega$ is bent into a circle. What is the equivalent resistance between two diametrically opposite points in $\Omega$?