Question

Two electric bulbs with 100 w power and other with 60 w power are connected in parallel whatt will be the current drawn when connected to 220 voltage

Answer 1

Given power of bulb 1 P₁ = 100 W and

power of bulb 2 P₂ = 60 W

Potential difference V = 220 V.

We know power P =V I -------(A) ; where I = current.

Also V = IR

I =V/R -----(B)

Reducing B in A we get,

P = V²/R

For 100 W bulb

R₁ = 220²/100

R₁ = 484 Ω

For 60 W bulb

R₂ = 220²/60

R₂ =  805.2 Ω

As mentioned in the question the bulb are connected in parallel setup its equivalent resistance will be

(1/Rₐ) = (1/R₁) +(1/R₂) ; where Rₐ = equivalent resistance

= (1/484)+(1/805.2)

Rₐ = (484 × 805.2)/(484 + 805.2)

Rₐ = 302.29 Ω

As mentioned earlier V=I R

I = V/Rₐ = 220/302.29

I = 0.72 Ampere