Numford

Heat and thermodynamicsClass 11, Thermal Properties of Matter

Dimensional formula of Heat flow rate

[M L2 T-3]

SI unitwatt (W)

Heat conducted per second. It has the dimension of power.

Derivation

How to get the dimensional formula of heat flow rate

  1. Start from the definition: heat flow rate = heat / time.
  2. velocity = length / time, so velocity is [L] / [T] = [L T-1].
  3. acceleration = velocity / time, so acceleration is [L T-1] / [T] = [L T-2].
  4. force = mass × acceleration, so force is [M] × [L T-2] = [M L T-2].
  5. displacement = length, so displacement is [L] = [L].
  6. work = force × displacement, so work is [M L T-2] × [L] = [M L2 T-2].
  7. heat = work, so heat is [M L2 T-2] = [M L2 T-2].
  8. Put in the dimension of each part: [M L2 T-2] / [T].
  9. Add the powers of each base quantity: [M L2 T-3].
Same dimensions

Quantities with the dimensions [M L² T⁻³]

Equal dimensions do not make them the same quantity. Compare heat flow rate with the others in the full grid.

Practice

Three questions on heat flow rate

1Which of these has the same dimensions as heat flow rate?

2What is the SI unit of heat flow rate?

3Do heat flow rate and heat have the same dimensions?

Questions

Heat flow rate: quick answers

What is the dimensional formula of heat flow rate?

The dimensional formula of heat flow rate is [M L² T⁻³]. It comes from heat flow rate = heat / time.

What is the SI unit of heat flow rate?

The SI unit of heat flow rate is the watt (W).

Which quantities have the same dimensions as heat flow rate?

Heat flow rate shares [M L² T⁻³] with power. Equal dimensions do not make them the same quantity.

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