(a) Here, potential difference across the bulb, $V = 200 \text{ V}$Power of the bulb, $P = 100 \text{ W}$As $P = \frac{V^2}{R}, \quad R = \frac{V^2}{P} = \frac{(200 \text{ V})^2}{100 \text{ W}}$$= \frac{4 \times 10^4}{100} \, \Omega = 400 \, \Omega$(b) Electric energy consumed by 1 bulb in 10 hours for 30 days, i.e.,$W = P t$$= 100 \text{ W} \times 10 \times 30$$= 30000 \text{ Wh}$Electric energy consumed by 3 bulbs$= 30000 \times 3$$= 90000 \text{ Wh}$$= 90 \text{ kWh}$$= 90 \text{ unit}$(c) Cost of 90 units of electric energy$= 90 \times 6.50 = \text{₹} 585 \text{ . }$ OR (a) Ohm's law states that current flowing through a conductor is directly proportional to the potential difference maintained across the two ends of a conductor at constant temperature and pressure.Let current flowing through a conductor is $I, V$ is the potential difference maintained across the two ends of conductor.As per Ohm's law, $V \propto I$Thus,$V = I R$Here $R$ is a proportionality constant called resistance. As per the question, the resistance of a conductor is $1 \text{ ohm}$.Let $V=1$ volt and $I=1 \text{ A}$, then $R=1 \text{ ohm}$ Hence, the resistance is said to be $1 \text{ ohm}$ if 1 ampere of current flows through a circuit due to the potential difference of 1 volt.(b) Electric power is the rate at which work is done or energy is transformed in an electrical circuit.The formula for electric power is given by:$P = V I$where,$P$ is the power$V$ is the potential difference in the circuit I is the electric currentPower can also be written as$P = I^2 R$$P = \frac{V^2}{R}$The above two expressions are got by using Ohms law, where, voltage, current and resistance are related by the following relation.Where,$R$ is the resistance in the circuit.$V$ is the potential difference in the circuit I is the electric current(c) For $x$ number of resistors of resistance $132 \, \Omega$Supply voltage, $V = 220 \text{ V}$Current, $I = 5 \text{ A}$Equivalent resistance of the combination $=R$, given as$\frac{1}{R} = x \times \frac{1}{132}$$R = \frac{132}{x}$From Ohm's law :$132 x = \frac{220}{5}$$132 x = 44$$132 = 44 x$$x = \frac{132}{44}$$x = 3$So, answer is 3 resistors.