Question

(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 1

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.