UPSEE 2019 Solved Paper

Key-Idea Power consumed by a electric device is given as
P=

V2

R

where, V= potential across device and
R= resistance of device
Here, V1=200V
P1=100W
and V2=100V
Resistance of bulb, R1=

V12

P1

⇒R1=

(200)2

100

=400Ω
Hence, the power consumed by bulb
P2=

V22

R2

[∵R1=R2]
⇒P2=

(100)2

400

=25W