# Resistivity in Electric Current – Class 10 Science Experiment

## Activity Name: Resistivity in Electric Current

### Activity Description:

The experiment aims to investigate the relationship between the cross-sectional area of a conductor and the current flowing through it to understand how resistance varies with the cross-sectional area.

### Required Items:

1. Iron rods of equal lengths but different cross-sectional areas
2. Circuit setup with an ammeter
3. Connecting wires
4. Power source

### Step by Step Procedure:

1. Collect iron rods of different cross-sectional areas but with the same length.
2. Set up the circuit as shown in figure 14.
3. Connect one of the iron rods between points P and Q in the circuit.
4. Note the value of the current using the ammeter and record it in your notebook.
5. Repeat the process with each of the other iron rods, noting the corresponding current values for each.
6. Observe that the current flowing through the rod increases with an increase in its cross-sectional area.
7. Based on the observations, conclude that the resistance of a conductor is inversely proportional to its cross-sectional area, i.e., R ∝ 1/A (at a constant temperature and length of the conductor).
8. From equations (1) and (2), deduce that R ∝ l/A (at a constant temperature) and R = ρl/A, where ρ is the resistivity (specific resistance) of the material.

### Experiment Observations:

Record the current values for each iron rod with different cross-sectional areas.

### Precautions:

1. Ensure all connections in the circuit are secure.
2. Use iron rods of equal length for accurate comparisons.
3. Take multiple readings to reduce errors and increase accuracy.
4. Use appropriate safety measures while working with electrical circuits.

### Lesson Learnt from Experiment:

The experiment demonstrates that the resistance of a conductor is inversely proportional to its cross-sectional area at a constant temperature. It also helps understand the concept of resistivity (ρ) as a material property, which influences a conductor’s resistance.