Question

A bulb is rated at 200v-100w.what is the resistance

Answer 1

Given :

• Power (P) = 100 W
• Potential Difference (V) = 200 V

To Find :

• Resistance of bulb

Solution :

We know that :

$\boxed{\sf{P\ =\ VI}} \: \: \: \: \: \sf{and} \: \: \: \: \: \boxed{\sf{V\ =\ IR}}$

Substituting, we get

⇒P = VI

⇒P = V * V/R

⇒P = V²/R

⇒100 = 200²/R

⇒100 = 40000/R

⇒R = 40000/100

⇒R = 400

∴ Resistance of Bulb is 400 Ω

Answer 2

Given ,

Potential difference (v) = 200 v

Electric power (P) = 100 w

We know that ,

Electric power is defined as the product of potential difference and current

$\boxed{ \sf{P = VI}}$

Thus ,

100 = 200 × I

I = 1/2

I = 0.5 amp

Now , the relationship between potential difference and current is given by

$\boxed{ \sf{V = IR}}$

Thus ,

200 = 0.5 × R

R = 200/0.5

R = 400 ohm

$\therefore$ The resistance is 400 Ω