Wheatstone bridge-1
5. Wheatstone Bridge
Location of Apparatus
Low voltage power supply
Wheatstone bridge
Resistance box
Unknown Resistance
Galvanometer
Wires
C 3rd shelf and 6th shelf
Top of shelf C
J 3rd shelf
W bottom shelf
I left 5th shelf
Set of wire needed:
How
many
4
Color
Length
Black
3
2
Black
Black
Very Short
(in the wire box)
Medium
Medium
Type
Banana
Banana
Banana & Flat
Head
Wheatstone bridge-2
2
1
Red
Red
Medium
Medium
Banana
Banana & Flat
Head
Notes
Keywords : Voltage divider, Null measurement, Problem of current drawn by the meters
Show inside the resistor box so that students to see how resistors are connected. Check if there is an
open resistor box is on the instructor’s table.
After have students connect the circuits check the wiring. Tell students not to turn on the power supply.
Make sure the voltage/current knobs are set to minimum before turn on the power. Voltage 2-3V is
sufficient.
When measurements are done make sure to have them turn off the switch to avoid burning the wire of
the bridge.
Try to balance near the center (50cm). Discuss why this is important. Estimate the difference in errors
comparing balancing the bridge at the center (about 50cm) and at the edge, about 1cm away from the
edge.
Do not drag the key.
Resistance of the unknown wire is about 62.5 ohms.