**1. What is electric current?**

**Answer:** Electric current is the flow of electric charge through a conductor, measured in amperes (A).

**2. Define drift velocity, mobility, and their relation with electric current.**

**Answer:** Drift velocity is the average velocity of charge carriers in a conductor due to an electric field. Mobility is the measure of how easily charge carriers can move through a material under the influence of an electric field. Electric current is directly proportional to drift velocity and mobility.

**3. State Ohm’s law.**

**Answer:** Ohm’s law states that the current passing through a conductor between two points is directly proportional to the voltage across the two points, given constant temperature.

**4. Explain electrical resistance.**

**Answer:** Electrical resistance is the property of a material that resists the flow of electric current. It is measured in ohms (Ω).

**5. Describe the V-I characteristics of ohmic and non-ohmic conductors.**

**Answer:** Ohmic conductors follow Ohm’s law, exhibiting a linear relationship between voltage and current. Non-ohmic conductors do not follow Ohm’s law and may have nonlinear V-I characteristics.

**6. What is electrical energy and power?**

**Answer:** Electrical energy is the work done by electric charges as they move through a circuit and is measured in joules (J). Electrical power is the rate at which electrical energy is transferred or consumed and is measured in watts (W).

**7. Define electrical resistivity and conductivity.**

**Answer:** Electrical resistivity is a measure of how strongly a material opposes the flow of electric current, measured in ohm-meters (Ω·m). Conductivity is the reciprocal of resistivity and measures how easily a material conducts electric current.

**8. Explain series and parallel combinations of resistors.**

**Answer:** In series combination, resistors are connected end-to-end, and the total resistance is the sum of individual resistances. In parallel combination, resistors are connected across the same two points, and the reciprocal of the total resistance is the sum of the reciprocals of individual resistances.

**9. Discuss the temperature dependence of resistance.**

**Answer:** Most conductors experience an increase in resistance with an increase in temperature due to increased collisions between charge carriers and atoms. However, semiconductor materials may exhibit decreased resistance with increasing temperature.

**10. What is internal resistance, potential difference, and EMF of a cell?**

**Answer:** Internal resistance is the inherent resistance within a cell to the flow of electric current. Potential difference is the voltage between two points in a circuit, while EMF (electromotive force) is the maximum potential difference between the terminals of a cell when no current is flowing.

**11. How are cells combined in series and parallel?**

**Answer:** Cells are combined in series by connecting the positive terminal of one cell to the negative terminal of another. In parallel combination, the positive terminals are connected together, and the negative terminals are connected together.

**12. What are Kirchhoff’s laws, and how are they applied?**

**Answer:** Kirchhoff’s laws are the Kirchhoff’s current law (KCL) and Kirchhoff’s voltage law (KVL). KCL states that the algebraic sum of currents entering and leaving a junction in a circuit is zero. KVL states that the sum of the electromotive forces and potential differences around any closed loop in a circuit is zero.

**13. Explain the Wheatstone bridge.**

**Answer:** The Wheatstone bridge is a circuit used to measure an unknown resistance by balancing it against known resistances. It consists of four resistors in a diamond shape, with a galvanometer connected across one diagonal and a battery across the other.

**14. What is a Meter Bridge?**

**Answer:** A Meter Bridge is a device used to measure the resistance of an unknown resistor by comparing it with a known resistance using a Wheatstone bridge setup.

**15. What is the significance of the Wheatstone bridge in electrical measurements?**

**Answer:** The Wheatstone bridge provides a precise and accurate method for measuring resistance, making it valuable in various electrical measurement applications.

**16. How does the resistance of a conductor change with temperature?**

**Answer:** In general, the resistance of conductors increases with temperature due to increased atomic vibrations that hinder the flow of electrons.

**17. Discuss the factors affecting the mobility of charge carriers in a material.**

**Answer:** Factors affecting the mobility of charge carriers include the type of material, temperature, impurities, and the presence of an external electric or magnetic field.

**18. Explain the concept of electrical conductivity.**

**Answer:** Electrical conductivity is a measure of how easily a material allows the flow of electric current. Materials with high conductivity allow current to flow easily, while materials with low conductivity resist the flow of current.

**19. What is the role of a resistor in an electric circuit?**

**Answer:** A resistor limits the flow of electric current in a circuit, controlling the amount of current and voltage across different parts of the circuit.

**20. How does the total resistance change when resistors are connected in series and parallel?**

**Answer:** In series connection, the total resistance is the sum of individual resistances. In parallel connection, the reciprocal of the total resistance is the sum of the reciprocals of individual resistances.