Low Cost Apparatus
Apparatus Title: Temperature Variation of Resistance
Abstract: A copper coil (60 - 100 ohms) wound over a copper tube is used to study the temperature variation of resistance. The coil is placed in a can of water and connected to ac voltage line for 10 min. The resistance of the coil is then measured with a multimeter as a function of temperature.
Equipment required to construct apparatus:
Item Source/store part number Cost ($)
Description Temperature Variation of Resistance
experimental system, shown in Fig.1, consists of a soup can (1), a nylon
can cover (4), a resistance coil (3), and a thermometer (8). The resistance
coil is made by winding 4-m long #32 insulated copper wire over a copper
pipe (6) with a diameter of 1.6-cm and a length of 15 cm. The copper wire
is between two Plexiglass rings (2) glued to the copper pipe. The Plexiglass
rings are 3 mm wide and they are cut from a Plexiglass tube with 1.6 mm
inner diameter and 2.2 mm outer diameter. The copper coil has a resistance
of 80 ohms. It is found that the coil resistance of 60-100 ohms is most
suitable for this experiment. The ends of the coil are connected to banana
plug sockets (5) fixed to the nylon cover. The copper pipe is also fixed
to the nylon cover. A thermometer (8), inserted in the copper pipe, is
resting on a copper support (7) hanging from the top of the copper pipe.
The bottom of the thermometer is approximately at the center of the coil.
Figure 2 shows the data obtained for a coil with a resistance of 60 ohms at room temperature. Obviously the resistance of the coil varies linearly with temperature and the temperature coefficient of resistance obtained from the experiment, 4.5 x 10-3 1/K, is very close to the accepted value.
Fig. 2 Resistance variation of a 60 ohm coil as a function of temperature.
The equipment described here can be easily constructed and the experiment can be performed in high school or college laboratories with good results. We have also used this equipment successfully with PASCO Science workshop 750 interface.