Home
Class 12
PHYSICS
If a 30 V, 90 W bulb is to be worked in ...

If a 30 V, 90 W bulb is to be worked in 120 V line, the resistance to be connected in series with the bulb is

A

`20Omega`

B

`10Omega`

C

`40Omega`

D

`30Omega`

Text Solution

Verified by Experts

The correct Answer is:
D
For 30V, 90W bulb
`R=(V^(2))/(P)=(30xx30)/(90)=10Omega,I=(P)/(V)=(90)/(30)=3A`
To work with 120V line, `3=(120)/(10+R)impliesR=30Omega`.
Promotional Banner

Topper's Solved these Questions

  • KARNATAKA CET 2002

    KCET PREVIOUS YEAR PAPERS|Exercise PHYSICS (MCQ.s)|60 Videos

  • KARNATAKA CET 2005

    KCET PREVIOUS YEAR PAPERS|Exercise PHYSICS|59 Videos

Similar Questions

Explore conceptually related problems

If a 30 V, 90 W bulb is to be worked in 120 V line, the resistance to be counnected in series with the bulb is

A milliammeter of range 10 mA has a coil of resistance 1Omega . To use it as a voltmeter of range 10V, the resistance that must be connected in series with it is

A battery of e.m.f. 12V and internal resistance 2Omega is connected in series with a tangent galvanometer of resistance 4Omega . The deflection is 60^@ when the plane of the coil is along the magnetic meridian. To get a deflection of 30^@ , the resistance to be connected in series with the tangent, galvanometer is :

With a resistance R connected in series with a galvanometer of resistance 100 Omega , it acts as a voltmeter of range 0-V. To double the range a resistance of 1000 Omega is to be connected in series with R. Then the value of R is ( Omega )

If ac supply is used and an iron core is introduced in a coil connected in series with the bulb, then what happens to the intensity of the bulb?

A 30 V, 90 W lamp is to be perated on a 120 V D.C. line. For proper glow, a resistor of ………….. ohm should be connected in series with the lamp.

A 60 V, 10 W lamp is to be run on 100 V, 60 Hz a.c. mains. Calculate the inductance of a chock required to be connected in series with it to work the bulb.

Two bulbs of wattages 25 and 100 respectively each rated at 220 V are connected in series with the supply of 440 V. Which bulb will fuse ?

An electric bulb has a rated power of 50 W at 100 V. It is used on an a.c. source 200 V, 50 Hz, a choke has to be used in series with it. The choke should have an inductance of

KCET PREVIOUS YEAR PAPERS-KARNATAKA CET 2003-PHYSICS
  1. A lamp hanging 4 metres above the table is lowered by 1 metre. Illumin...

    Text Solution

    |

  2. Two wires of the same dimensions but resistivities rho(1) and rho(2) a...

    Text Solution

    |

  3. If a 30 V, 90 W bulb is to be worked in 120 V line, the resistance to ...

    Text Solution

    |

  4. The potential difference between the terminals of a cell in open circu...

    Text Solution

    |

  5. Thirteen resistances each of resistance R ohm are connected in the cir...

    Text Solution

    |

  6. A group of N cells whose e.m.f. varies directly with the internal resi...

    Text Solution

    |

  7. The dimensions of a/b in the equation P=(a-t^(2))/(bx) where P is pres...

    Text Solution

    |

  8. Three vectors satisfyi the relation vecA*vecB=0 and vecA*vecC=0 then v...

    Text Solution

    |

  9. A student is standing at a distance of 50 metre from the bus. As soon ...

    Text Solution

    |

  10. For a given velocity, a projectile has the same range R for two angles...

    Text Solution

    |

  11. Weight of a body of mass m decreases by 1% when it is raised to height...

    Text Solution

    |

  12. The equation of a transverse wave travelling along positive x axis wit...

    Text Solution

    |

  13. If v(m) is the velocity of sound in moist air, v(d) is the velocity of...

    Text Solution

    |

  14. if T is the reverberation time of an auditorium of volume V, then

    Text Solution

    |

  15. Two wires are fixed in a sonometer. Their tensions are in the ratio 8:...

    Text Solution

    |

  16. A sound source is moving towards stationary listener with (1)/(10)th o...

    Text Solution

    |

  17. If v is the speed of sound in air then the shortest length of the clos...

    Text Solution

    |

  18. Cavitation is a special application property exhibited only by

    Text Solution

    |

  19. In Young's double slit experiment, the fringe width is beta. If the en...

    Text Solution

    |

  20. Yellow light is used in signel slit diffraction experiment with slit w...

    Text Solution

    |