The out-of-balance Wheatstone
bridge - applications
Aim - To investigate
several applications of the Wheatstone bridge in the out-of-balance condition.
Instructions
The Wheatstone bridge is balanced.
Place the LDR in a dark place and note the current on the micro-ammeter.
Place the LDR in a light place and note the current on the micro-ammeter.
Explain why the current is greater than zero for one condition and less than zero for
the other.
Replace the LDR with the thermistor.
The Wheatstone bridge is balanced when the thermistor
is in melting ice.
Place the probe in the boiling water by clicking on the text "Boiling water at 100 oC".
Note the current on the micro-ammeter.
Predict the current that will be obtained when the probe is at room temperature.
Test your prediction. What assumptions are you making about the temperature of the
probe, its resistance, and the out-of-balance current?
Replace the thermistor with two strain gauges connected in the two arms of the
wheatstone bridge as shown.
Click above the right end of the hacksaw blade to push it down. Click below to
push it up.
Note the out-of balance current.
Explain how the out-of-balance current is used to show:
a) the amount of bending / strain put on the hacksaw blade
b) the direction of the bending / strain put on the hacksaw blade.