$A$ metal has a very large number of free electrons and a non-metal has a very small number of free electrons.

Derive the relation $R = R_{1} + R_{2} + R_{3}$ when three resistors $R_{1}, R_{2}$ and $R_{3}$ are connected in series in an electric circuit.

$A$ $4 \, \Omega$ resistance wire is doubled on itself. Calculate the new resistance of the wire.

Which of the following represents Ohm's law?

The electrical resistivity of a few materials is given below in ohm-metre. Which of these materials can be used for making the element of a heating device?

$A$. $6.84 \times 10^{-8} \, \Omega m$

$B$. $1.60 \times 10^{-8} \, \Omega m$

$C$. $1.00 \times 10^{-4} \, \Omega m$

$D$. $2.50 \times 10^{12} \, \Omega m$

$E$. $4.40 \times 10^{-5} \, \Omega m$

$F$. $2.30 \times 10^{17} \, \Omega m$

Five bulbs are connected in a series circuit. If the third bulb in the middle blows out,what happens?