(a) An electric blub is rated at 200 V; 100 W. What is its resistance?

1.	(a) An electric blub is rated at 200 V; 100 W. What is its resistance?(b) Calculate the energy consumed by 3 such bulbs if they glow continuously for 10 hours for complete month of November.(c) Calculate the total cost if the rate is rupees 6.50 per unit
Answer» Answer :- (a) An electric blub is rated at 200 V; 100 W. What is its RESISTANCE? = Here, Potential difference (V) = 220 V Electric power (P) = 100 W We know that, $\boxed{\star{\sf R = \dfrac{{V}^{2}}{P}}}$ $\sf\longrightarrow R = \dfrac{{(220)}^{2}}{100}$ $\sf\longrightarrow R = \dfrac{220 \times 220}{100}$ $\sf\longrightarrow R = 484 \Omega$ Hence, the resistance of the bulb rated 220V ; 100W is 484 Ω. (B) Calculate the energy consumed by 3 such bulbs if they glow continuously for 10 hours for complete month of November. = Here, No. of bulbs = 3 Amount of time = 10 hours No. of days = 30 days Electric power (P) = 100 W Then, total consumption of electrical energy for the THREE bulbs :- = (3 × 10 × 30 × 100) watt-hour = 90000 Wh To convert it into kilo-watt hour or BOT unit, we've to divide it by 1000. .°. 90000/1000 kWh = 90 BOT unit. Hence, the total electric energy consumed in 30 days will be 90 BOT unit. (c) Calculate the total cost if the rate is rupees 6.50 per unit. = Here, Total energy consumed = 90 BOT unit. Cost of energy per unit = Rs. 6.50 .°. Total cost = Rs. (90 × 6.50) = Rs. 585 Hence, the total cost is Rs. 585 per month.