$A$ $100 \text{ W}$ electric bulb is lighted for $2 \text{ hours}$ daily,and four $40 \text{ W}$ bulbs are lighted for $4 \text{ hours}$ everyday. Calculate the energy consumed (in $\text{kWh}$) in $30 \text{ days}$.

Why are alloys commonly used in electrical heating devices?

How can we measure the current in a circuit?

State $Ohm's$ law. Calculate the resistance of a conductor,if the current flowing through it is $0.2 \, A$ when the applied potential difference is $0.8 \, V$.

$(a)$ In the circuit shown, connect a nichrome wire of length $L$ between points $X$ and $Y$ and note the ammeter reading.
$(i)$ When this experiment is repeated by inserting another nichrome wire of the same thickness but twice the length $(2L)$, what changes are observed in the ammeter reading?
$(ii)$ State the changes that are observed in the ammeter reading if we double the area of cross-section without changing the length in the above experiment. Justify your answer in both cases.
$(b)$ "Potential difference between points $A$ and $B$ in an electric field is $1\, V$." Explain the statement.

How can we measure the potential difference across the ends of a conductor?