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Engineering
92 Views   |

If a wire of resistance 20Ω is covered with ice and a voltage of 210 V is applied across the wire, then the rate of melting of ice is

• Option 1)

0.85g/s

• Option 2)

1.92g/s

• Option 3)

6.56g/s

• Option 4)

none of these

As we learnt in  Power dissipiated in external resistance - -    Rate of energy produces Energy required to melt one gm of ice = mL = 1   80  4.2 J = 336J/g      Rate of ice melting =  Option 1) 0.85g/s Incorrect Option 2) 1.92g/s Incorrect Option 3) 6.56g/s Correct Option 4) none of these Incorrect
Engineering
87 Views   |

An immersion heater is rated 836 watt. It should heat 1 litre of water from $10^{0}C$ to $40^{0}C$ in about

• Option 1)

200 sec

• Option 2)

150 sec

• Option 3)

100 sec

• Option 4)

120 sec

As we learnt in  Power dissipated in external resistance - -     Amount of energy required = m s  T                                            = 1 kg  (4.18 J/g)  30                                           = 4180  30J= 125400J Time required =                         Option 1) 200 sec Incorrect Option 2) 150 sec Correct Option 3) 100 sec Incorrect Option 4) 120 sec Incorrect
Engineering
119 Views   |

An electric kettle takes 4 A current at 220 V. How much time will it take to boil 1 kg of water from room temperature $20^{0}C$? The temperature of boiling water is $100^{0}C$

• Option 1)

6.4 minutes

• Option 2)

6.3 minute

• Option 3)

12.6 minutes

• Option 4)

12.8 minutes

As we learnt in  Power dissipated in external resistance - -    Total energy required = m s T = 1000  1 cal/g  80 = 80000  4.2 J = 336000J   Option 1) 6.4 minutes Incorrect Option 2) 6.3 minute correct Option 3) 12.6 minutes Incorrect Option 4) 12.8 minutes Incorrect
Engineering
562 Views   |

A house is served by 220 V supply line in a circuit protected by a 9 ampere fuse. The maximum number of 60 W lamps in parallel that can be turned on, is

• Option 1)

44

• Option 2)

20

• Option 3)

22

• Option 4)

33

As we learnt in  Series Grouping - In series grouping anode of one cell is connected to cathode of other cell - wherein    Maximum power = 220   9W  number of Bulb  =  Option 1) 44 Incorrect option Option 2) 20 Incorrect option Option 3) 22 Incorrect option Option 4) 33 Correct option
Engineering
98 Views   |

A heater of 220 V heats a volume of water in 5 minute time. A heater of 110 V heats the same volume of water in

• Option 1)

5 minutes

• Option 2)

8 minutes

• Option 3)

10 minutes

• Option 4)

20 minutes

As we learnt in Power dissipiated in external resistance - -     Energy = P . t Initial energy = Final energy    Option 1) 5 minutes Incorrect Option Option 2) 8 minutes Incorrect Option Option 3) 10 minutes Incorrect Option Option 4) 20 minutes Correct Option
Engineering
393 Views   |

A 500 W heating unit is designed to operate from a 115 volt line. If the line voltage drops to 110 volt, the percentage drop in heat output will be

• Option 1)

10.2%

• Option 2)

8.1%

• Option 3)

8.6%

• Option 4)

7.6%

As we learnt in Power dissipiated in external resistance - -     Change                   Option 1) 10.2% Incorrect Option 2) 8.1% Incorrect  Option 3) 8.6% Correct  Option 4) 7.6% Incorrect
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