Q&A - Ask Doubts and Get Answers

Sort by :
Clear All
Q
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 
Exams
Articles
Questions