Pasco TD-8513 Heat Conduction Apparatus User Manual download pdf (Page 10)

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Heat Conduction Apparatus Experiment #2: Angstrom’s Method

10

According to Angstrom’s method

where n is the harmonic, ω is the driving frequency, and ∆x is the distance between

the thermistors.

In this experiment, the driving frequency is very small so it is easier to consider the

period (T) of the wave, where

The time delay (∆t) between the two waves is measured directly. The relative phase,

(φ), is calculated using

where T

n

is the period of the harmonic. Thus

Combining these four equations yields

Note that α is independent of the harmonic (n) and of the driving frequency (ω).

A more commonly used quantity that is related to the thermal diffusivity, but includes

the specific heat (c) and density (ρ) of the material, is the thermal conductivity (k).

This gives the final expression:

α

nω x∆()

2

2φ ln

A

c

A

f

------

------------------------=

ω

2π

T

------=

φ 2π

t∆

T

n

-----

=

T

n

T

n

---

=

α

x

2

∆

2 t ln

A

c

A

f

------

∆

---------------------------

=

kcρα=

k

cρα x∆()

2

2 t ln

A

c

A

f

------

∆

---------------------------

=

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