Procedure

Apparatus

carey foster bridge, unknown low resistor, Resistance box, Lead accumulator, jockey, one way key, Galvanometer, connecting wires etc.

Procedure to perform the simulation

To calibrate the Carey Fosters Bridge

1. Drag the "Resistor" to the gap 2 and 3 of the Carey fosters bridge.
2. Drag “Fractional resistor" to gap 1.
3. Drag the Battery to space in between the two “Resistors".
4. Drag the copper strip to gap 4.
5. Press the continue button, on the top.
6. Click and unmark the resistance which has to be introduced in “Resistor".
7. Power On button to start and power off to stop the experiment.
8. Change the position of jockey to get balancing length l₁.
9. Reverse connection button to interchange copper strip with fractional resistor.
10. Move jockey to get balancing length l₂.
11. Resistance per cm of bridge wire is found using equation

$$\rho=\frac{r}{\acute{l_{1}}-\acute{l_{2}}}$$

13. Repeat the experiment for different values of Resistance.

To find the temperature coefficient of resistance

1. Repeat steps 1-3 from the previous procedure.
2. Drag "Unknown resistance 1" to gap 4 in bridge.
3. Introduce the resistance and move jockey to get balancing length l₁.
4. Reverse button to interchange unknown resistance 1 with Fractional resistor.
5. Move jockey to get balancing length l₂.
6. Unknown resistance value is found using the equation

$$X=R+\rho(l_{1}-l_{2})$$

7. Repeat the experiment for different temperature t1, t2...and note the corresponding resistance X1, X2...
8. Temperature coefficient of resistance is found using equation

$$\alpha=\frac{X_{2}-X_{1}}{X_{1}t_{2}-X_{2}t_{1}}$$

9. Repeat the experiment for unknown resistance 2.
10. A graph is plotted between values of X and t , which gives a straight line, whose slope is equal to α.