If three bulbs of $100 \; W$, $60 \; W$, and $40 \; W$ are used for $2 \; \text{hours}$ daily in a house, how many units of electrical energy are consumed in $30 \; \text{days}$?

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

What is the unit of electric potential difference?

What is Joule's heating effect? How can it be demonstrated experimentally? List its four applications in daily life.

Define resistance of a conductor. State the factors on which resistance of a conductor depends. Name the device which is often used to change the resistance without changing the voltage source in an electric circuit.
Calculate the resistance of $50 \, m$ length of wire of cross-sectional area $0.01 \, mm^2$ and of resistivity $5 \times 10^{-8} \, \Omega \, m$.

What type of electric charge does an electron possess?