Physics, asked by spbijalwan001, 7 months ago

Q.One lamp of 90 watt and 30 volt has to be used in a line of 120 volt. Lamp must be used with a residence-
1. 10 ohm in series
2. 20 ohm in parallel
3. 20 ohm in series
4. 10 ohm in parallel​

Answers

Answered by rakshit9847
0

Answer:

Resistance of lamp

R

0

=

P

V

2

=

90

(30)

2

=10Ω

Current in the lamp

I=

R

0

V

=

10

30

=3A

As the lamp is operated on 120V DC, then resistance becomes

R

=

i

V

=

3

120

=40Ω

For proper glow, a resistance R is joined in series with the bul

R

=R+R

0

⇒R

α

=R

−R

0

=40−10=30Ω

Answered by mdchaidabu123
1

Answer:

30V- 90w is operated in 120v line

Explanation:

Resostance of the lamp

R•= V^2/P

= (30)^2/90

= 900/ 90

= 10 ohm

Current in the lamp

I = V/R•

= 30/10 A

= 3A

As the lamp opereted at 120V DC

R' = V'/i

=120/3

= 40 ohm

There fore R' =R^ + R•

There fore R^ = R' - R•

= 40- 10

= 30 ohm

30 ohm is the correct answer, but it is not given. in the option

Thank you

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