Chapter Name: Electric Current
Activity Name: Resistivity in Electric Current
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.
- Iron rods of equal lengths but different cross-sectional areas
- Circuit setup with an ammeter
- Connecting wires
- Power source
Step by Step Procedure:
- Collect iron rods of different cross-sectional areas but with the same length.
- Set up the circuit as shown in figure 14.
- Connect one of the iron rods between points P and Q in the circuit.
- Note the value of the current using the ammeter and record it in your notebook.
- Repeat the process with each of the other iron rods, noting the corresponding current values for each.
- Observe that the current flowing through the rod increases with an increase in its cross-sectional area.
- 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).
- 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.
Record the current values for each iron rod with different cross-sectional areas.
- Ensure all connections in the circuit are secure.
- Use iron rods of equal length for accurate comparisons.
- Take multiple readings to reduce errors and increase accuracy.
- 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.