Question

A bulb is rated (10 W, 200 V). If this bulb is connected with 20 V supply, what is the current (in mA) through the electrical circuit ?​

Answer 1

In your question,

Power = 10w

voltage = 200v

power = current × voltage

P = VI or P = v²/R

then,

10 = 200× I

10/200 = I

1/20 or 0.05 A is current

and

P= V²/R

10 = 200²/R

R = 40000/10

R = 4000 ohms

now the bulb is connected to the 20 v

then,

10 = 20 × l

l =20/10

l = 2 A and 0.002mA

second sum is for extra information...