side of the thin (75-m) metal and dielectric belts slid-
50
5
off
T1
exceed 1C; hence, general melting of the ice cylinder
40
4
surface did not take place, although there may have been
some local melting at a few points of direct iceslider
3
30
contact.
Significant frictional electrification was found for all
sliding materials used (e.g., Fig. 3 and 4). The potential
20
2
differences V observed were comparable both when the
belt slid on its own circular track on the ice cylinder's
V
10
1
surface and when it slid continuously on a fresh surface
(spiral track). The electrification of the ice surface was
on
not homogeneous. Normally, it was possible to find two
0
0
positions along the 30-cm-long cylinder where V dif-
0
20
40
60
80
100
Time (s)
fered by a factor of two. Since the belt covered many ice
Figure 3. Potential difference V across 75-m-thick
grains, contributions from individual grains were not
significant and added only a small oscillating compo-
polyethylene film and its tension T (after Petrenko
nent to V.
and Colbeck 1994). Sliding velocity was 1 m/s. The
Typically, the potential differences generated be-
arrows indicate when the lathe was switched on and
off. Temperature was 19C.
tween ice and metal were about 300 V (ice/Al, 31.5C,
2 m/s). Under the same experimental conditions, the
300
off
electrical field generated by the friction of ice on poly-
off
off
240
was calculated as the ratio of the potential difference
across the film to the film thickness L. When the electri-
fication was measured in the temperature interval from
180
4.5 to 35C and for sliding velocities from 0.5 to 8
m/s, the sliders always received a positive charge. The
120
electrification increased with decreasing temperature
and increasing sliding velocity (Fig. 5). The maximum
60
V = 1.6 kV was found at the lowest temperature
T = 35C and the highest sliding velocity ν =8 m/s.
on
on
on
From the measurements of a current I passing
0
0
20
40
60
80
100
through the electrometer when it was used as a current
Time (s)
meter, we found that the coupled iceslider acted as a
Figure 4. Potential difference V between ice
charge generator (Fig. 6). Moreover, at temperatures
and a stainless foil. Sliding velocity was 1 m/s
above approximately 12C, the current is proportional
(after Petrenko and Colbeck 1994). Tempera-
ture is 30C. The arrows indicate when the
4
lathe was switched on and off.
3
50
40
2
30
1
T = 10 C
20
0
T = 14 C
10
1
T = 25 C
0
0
1
2
3
4
5
6
2
1
0
1
2
v (m/s)
ln[v(m/s)]
Figure 5. Dependence of the potential differ-
Figure 6. Dependence of the electric current
ence between ice and stainless steel slider on
though ice/metal slider interface on sliding
sliding velocity (after Petrenko and Colbeck
velocity at three different temperatures (after
1994). T = 10C.
Petrenko and Colbeck 1994).
4
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