Turn on thread page Beta
    • Thread Starter
    Offline

    0
    ReputationRep:
    A heating coil is usedx to warm water that flows past it at a steady rate of 0.24 kgs-1. The heating coil remains at a constant working temperature of 350 degrees. the cold wtaer enters at 17 degrees and leaved at 19 degrres. The specific capacity of water is 4200 J kg-1K-1. Calculate the rate of absorption of energy by the cold water assuming no energy is lost to the surroundings.

    HELP ME PLEASE!!
    Offline

    1
    ReputationRep:
    energy supplied to substance = mass * change in temp. * specific heat capacity

    You want the rate of absorption of energy, ie the amount of energy per secound supplied. You have the mass in terms of mass per s so you just need to multiply them I think.

    0.24*4200*2
    =2016JS^-1

    however dont trust me totally on this as its a year since I did any work on specific heat capacity.
    • Thread Starter
    Offline

    0
    ReputationRep:
    any help is better than none! thanks
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by Speciez99)
    energy supplied to substance = mass * change in temp. * specific heat capacity

    You want the rate of absorption of energy, ie the amount of energy per secound supplied. You have the mass in terms of mass per s so you just need to multiply them I think.

    0.24*4200*2
    =2016JS^-1

    however dont trust me totally on this as its a year since I did any work on specific heat capacity.

    why do i need to mulitply it by 2 though?
    Offline

    15
    ReputationRep:
    becasue of the 2 *C temperature rise.
    Offline

    16
    ReputationRep:


    H/s = m/s c delta T

    therefore H = 0.24 kg x 4200 J kg-1K-1 x (2 Kelvin)

    H = 2016 Joules

    Notice the seconds cancel out and your final answer is in joules.
    Offline

    15
    ReputationRep:
    rate of absorbtion of energy has to be in joules per second.
    Offline

    16
    ReputationRep:
    Nope

    You have to cancel out the seconds and have it in only joules.

    Says so in the marks scheme
    Offline

    15
    ReputationRep:
    let R = rate of absorbtion of energy

    E = m.c.T

    R = E/s = m/s.c.T

    you do not cancel out the seconds, because you are looking for E and not H.

    the mark scheme is wrong (or confused)
 
 
 

University open days

  • University of Bradford
    All faculties Undergraduate
    Wed, 21 Nov '18
  • Buckinghamshire New University
    All Faculties Postgraduate
    Wed, 21 Nov '18
  • Heriot-Watt University
    All Schools Postgraduate
    Wed, 21 Nov '18
Poll
Black Friday: Yay or Nay?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.