Question

An electric lamp is marked 100W,220V' what do u understand by this? What current is taken by the lamp when it is connected to a 220v mains supply? What is the resistance of the lamp

Answer 1

An electric lamp is marked 100 W, 220 V. It means that the electric lamp will consume 100 joule of energy per second when connected to a 220 V supply.

Given that the electric lamp is connected to a exactly 220 V mains supply.

So, We have

• Potential difference, V = 220 v
• Power, P = 100 W

The current passing through the electric lamp can be calculated as,

⇒ P = V I

Where,

• P = Power
• V = Potential difference
• I = Current

⇒ 100 = 220 × I

⇒ 10/22 = I

⇒ 5/11 = I

⇒ I = 5/11 A

Now, We have to find the resistance of the electric lamp, We have

• Potential difference, V = 220 v
• Current, I = 5/11 A

So, Resistance of the electric lamp can be calculated as,

⇒ V = I R

Where,

• R = Resistance

⇒ 220 = 5/11 × R

⇒ 220 × 11/5 = R

⇒ 44 × 11 = R

⇒ R = 484 Ω

Hence, When the electric lamp is connected to a 220 v mains supply,

• Current drawn = 5/11 A
• Resistance = 484 Ω

Answer 2

An electric lamp is marked 100 W, 220 V. It means that the electric lamp will consume 100 joule of energy per second when connected to a 220 V supply. Given that the electric lamp is connected to a exactly 220 V mains supply.