What is the unit of $Watt-second$?

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 $30 \; \text{days}$?

Draw a labelled circuit diagram showing three resistors $R_{1}, R_{2}$ and $R_{3}$ connected in series with a battery $(E)$,a rheostat $(Rh)$,a plug key $(K)$ and an ammeter $(A)$ using standard circuit symbols. Use this circuit to show that the same current flows through every part of the circuit. List two precautions you would observe while performing the experiment.

$(a)$ What is meant by saying that the potential difference between two points is $1$ volt?
$(b)$ Why does the connecting cord of an electrical heater not glow while the heating element does?
$(c)$ Electrical resistivities of some substances at $20^{\circ}C$ are given below:

Silver	$1.60 \times 10^{-8} \, \Omega m$
Copper	$1.62 \times 10^{-8} \, \Omega m$
Tungsten	$5.2 \times 10^{-8} \, \Omega m$
Iron	$10.0 \times 10^{-8} \, \Omega m$
Mercury	$94.0 \times 10^{-8} \, \Omega m$
Nichrome	$100 \times 10^{-6} \, \Omega m$

Answer the following questions in relation to them:
$(i)$ Among silver and copper, which one is a better conductor? Why?
$(ii)$ Which material would you advise to use in electrical heating devices? Why?

How much work is done in moving a charge of $2 \ C$ from a point at $118 \ V$ to a point at $128 \ V$ (in $J$)?

Three incandescent bulbs of $100\, W$ each are connected in series in an electric circuit. In another circuit,another set of three bulbs of the same wattage are connected in parallel to the same source. Now,if one bulb in both the circuits gets fused,will the rest of the bulbs continue to glow in each circuit? Give reasons.