Question

Write any three differences between electromotive force and potential difference.
OR
Write any three differences between Resistance and Specific Resistance.

Hint:

The resistance depends on the material's resistivity, the length of the conductor, and the cross-sectional area. Resistivity is an intrinsic property of materials and is independent of size and shape.

Answer 1

a. Differences Between Electromotive Force (emf) and Potential Difference (pd):
1. Definition:
- Electromotive Force (emf): emf is the energy supplied by a source (such as a battery or generator) per unit charge to move charges through a circuit. It is responsible for driving the current in the circuit.
- Potential Difference (pd): pd is the difference in electric potential between two points in a circuit. It represents the energy required to move a unit charge between two points in the circuit.
2. Cause:
- Electromotive Force (emf): It is caused by an energy source like a battery or generator, where chemical, mechanical, or thermal energy is converted into electrical energy.
- Potential Difference (pd): pd is caused by the resistance in the circuit and represents the work done by the electric field to move charges.
3. Measurement:
- Electromotive Force (emf): emf is measured in volts (V), and it is the work done per unit charge to move the charge through the complete circuit (when no current is flowing).
- Potential Difference (pd): pd is also measured in volts (V), and it is the work done per unit charge between two points in a closed circuit (when current is flowing).
b. Differences Between Resistance and Specific Resistance:
1. Definition:
- Resistance (R): Resistance is the opposition that a material offers to the flow of electric current. It depends on the material, shape, and size of the conductor.
- Specific Resistance (Resistivity, \( \rho \)): Specific resistance, or resistivity, is a property of the material that quantifies its intrinsic resistance to electric current. It is independent of the size and shape of the conductor.
2. Formula:
- Resistance (R): The formula for resistance is given by \( R = \rho \frac{L}{A} \), where \( L \) is the length of the conductor, \( A \) is the cross-sectional area, and \( \rho \) is the specific resistance (resistivity).
- Specific Resistance (Resistivity, \( \rho \)): Resistivity is represented by \( \rho = R \frac{A}{L} \), where \( R \) is the resistance, \( A \) is the area, and \( L \) is the length of the conductor.
3. Units:
- Resistance (R): The unit of resistance is ohms (\( \Omega \)).
- Specific Resistance (Resistivity, \( \rho \)): The unit of specific resistance is ohm-meter (\( \Omega \, \text{m} \)).