3B Scientific Heat Equivalent Apparatus - Manual (Page 5)

5
Instruction sheet
3B SCIENTIFIC 3B SCIENTIFIC 3B SCIENTIFIC 3B SCIENTIFIC 3B SCIENTIFIC® PHYSICS PHYSICS PHYSICS PHYSICS PHYSICS
U10365 Equivalent of heat apparatus
U10366 Copper cylinder
®
9/04 MH
1 Base with conversion table for
resistance
→
temperature
2 Counter
3 Copper cylinder (U10366)
4 Electrical heating element
5 Hand crank
6 Table clamp
7 Knurled screw
8 Friction cord with counterweight (not visible)
9 Aluminum cylinder
bl Temperature sensor
bm Adapter cable
bn Bucket, 5 (not shown)
1
3 4
5 6 8 9 7 bl bm
2
Fig.1: Components
The equivalent of heat apparatus allows mechanical
work (measured in Nm) and electrical energy (measured
in Ws) to be converted into heat (measured in J). The
evaluation shows that all three forms of energy are
equivalent.
1. Safety instructions
•
Risk of injury! The (approx. 5 g) weight attached to
the cord 8 can cause injury to persons if it falls on
them. It should be placed on the ground to secure
it and not be raised more than about 10 cm during
the experiment.
•
Risk of burning! During the experiments the fric-
tion cylinder ( 3 or 9 ) is heated. It should be ob-
served that the temperature does not rise above
about 40°C. The maximum permissible current
through the heating element is 3 A and may not be
exceeded.
•
Risk of electric shock! The maximum output volt-
age of the power supply used for the electric heat-
ing may not be greater than 40 V.
2. Description, technical data
The equivalent of heat apparatus can be used to show
the equivalence of mechanical work due to friction
(Nm), electrical energy (Ws) and heat (J). The values
measured in Nm or Ws agree to an accuracy of about
2%. If this equivalence is assumed, the specific heat
capacity of aluminum and copper can be determined.
The stable design with its integrated rotary counter and
a dual ball-bearing mounted shaft make experiments
as simple as possible to perform. To measure tempera-
ture a negative temperature coefficient thermistor (NTC)
is used. This is safely contained inside an aluminum
sleeve. The aluminum sleeve snaps into the friction
cylinder so that it cannot slide out unintentionally.
Technical data for the friction cylinder (approximate
values):
Diameter D:
48 mm
Height: 50 mm
Aluminum cylinder: mass m
A
= 250 g,
specific heat capacity
c
A
= 0.86 kJ/kg K,
Copper cylinder: m
K
= 750 g, c
K
= 0.41 kJ/kg K
Electrical connection: sockets of 2 mm diameter,
positive pole “+” isolated,
negative pole “–” connected to
ground, reversal of polarity
does not destroy the
equipment.