vacua
vacuum 的复数形
vacuum 的复数形
Vacuum \
Vac "
u *
um \ (
v [
a ^]
k "[-
u ]*[
u ^]
m ),
n .;
pl .
E . {
Vacuums }
(
v [
a ^]
k "[-
u ]*[
u ^]
mz ),
L . {
Vacua } (
v [
a ^]
k "[-
u ]*[.
a ]). [
L .,
fr .
vacuus empty .
See {
Vacuous }.]
1 . (
Physics )
A space entirely devoid of matter (
called also ,
by way of distinction ,
absolute vacuum );
hence ,
in a more general sense ,
a space ,
as the interior of a closed vessel ,
which has been exhausted to a high or the highest degree by an air pump or other artificial means ;
as ,
water boils at a reduced temperature in a vacuum .
[
1913 Webster ]
[
1913 Webster ]
2 .
The condition of rarefaction ,
or reduction of pressure below that of the atmosphere ,
in a vessel ,
as the condenser of a steam engine ,
which is nearly exhausted of air or steam ,
etc .;
as ,
a vacuum of 26 inches of mercury ,
or 13 pounds per square inch .
[
1913 Webster ]
{
Vacuum brake },
a kind of continuous brake operated by exhausting the air from some appliance under each car ,
and so causing the pressure of the atmosphere to apply the brakes .
{
Vacuum pan } (
Technol .),
a kind of large closed metallic retort used in sugar making for boiling down sirup .
It is so connected with an exhausting apparatus that a partial vacuum is formed within .
This allows the evaporation and concentration to take place at a lower atmospheric pressure and hence also at a lower temperature ,
which largely obviates the danger of burning the sugar ,
and shortens the process .
{
Vacuum pump }.
Same as {
Pulsometer },
1 .
{
Vacuum tube } (
Phys .),
(
a )
a glass tube provided with platinum electrodes and exhausted ,
for the passage of the electrical discharge ;
a Geissler tube .
(
a )
any tube used in electronic devices ,
containing a vacuum and used to control the flow of electrons in a circuit ,
as a vacuum diode ,
triode ,
tetrode ,
or pentode .
{
Vacuum valve },
a safety valve opening inward to admit air to a vessel in which the pressure is less than that of the atmosphere ,
in order to prevent collapse .
{
Torricellian vacuum }.
See under {
Torricellian }.
[
1913 Webster ]
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