18.7 Applications of Kirchhoff's Rules Wheatstone Bridge |
| Instructions: Click on the "Start Simulation" button to open the applet window. Change the multimeter setting to an ammeter mode by sliding the blue knob to the right until it reads 25 Amp. Click on the positive lead of the multimeter and drag it to a point in the circuit between R1 and R2. Drag the negative lead to a point between Rx and R4. Move the blue knob in the multimeter to the left one notch at a time until the meter registers a value other than zero. Change the value of R2 by dragging the slider positioned above it until the meter reads zero. Move the blue knob on the multimeter to the 1 Amp position and readjust R2 until you get zero. The bridge is now balanced. Use the value of R2 along with the values of R1 and R4 to calculate Rx. Use the input box to verify your answer. You can also set the value of R2 by directly inputting the value in the provided box. Note that you can use the multimeter to measure the current and voltage anywhere in the circuit. Navigation: You can come back to this window by pressing the "Close Simulation" button on the bottom frame of the utility. |
| Explanation: The Wheatstone bridge is used to determine an unknown resistance (Rx in this case) by adjusting a known resistance (R2) until the measured current across the bridge is zero. As shown in problems 18.42 and 18.43, the unknown resistance is given by Rx=(R1/R2)*R4 |
| Source: Dorothea Wiarda Go to the web site and link to the Online Library for further information. |