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Questions and answers ❓❓
What is electric current, and how is it defined?
Answer: Electric current is the flow of electric charge through a conductor. It is defined as the rate of flow of charge through a cross-sectional area.
Explain Ohm’s Law in terms of potential difference and current.
Answer: Ohm’s Law states that the current flowing through a conductor is directly proportional to the potential difference across its ends, provided the temperature remains constant.
What are the factors affecting the resistance of a conductor?
Answer: The resistance of a conductor depends on its length, cross-sectional area, material, and temperature.
How does the resistivity of a material vary with temperature?
Answer: For most conductors, resistivity increases with an increase in temperature, whereas, for semiconductors, resistivity decreases with an increase in temperature.
What is the significance of Kirchhoff’s first law (junction rule)?
Answer: Kirchhoff’s first law states that the total current entering a junction equals the total current leaving the junction. This law is based on the conservation of charge.
Explain the concept of drift velocity in a conductor.
Answer: Drift velocity is the average velocity of free electrons in a conductor under the influence of an electric field.
What is the role of a battery in an electric circuit?
Answer: A battery provides the necessary potential difference (electromotive force) to drive the electric current through the circuit.
Describe the difference between conductors, insulators, and semiconductors in terms of resistivity.
Answer: Conductors have low resistivity, allowing easy flow of current. Insulators have high resistivity, preventing current flow. Semiconductors have resistivity between conductors and insulators, and their conductivity can be modified.
How do you define electrical resistivity?
Answer: Electrical resistivity is a material property that quantifies how strongly a material opposes the flow of electric current. It is the resistance per unit length and unit cross-sectional area.
What is the purpose of a resistor in an electric circuit?
Answer: A resistor is used to control or limit the flow of electric current in a circuit.
What happens to the total resistance when resistors are connected in series?
Answer: The total resistance increases when resistors are connected in series, as it is the sum of individual resistances.
What happens to the total resistance when resistors are connected in parallel?
Answer: The total resistance decreases when resistors are connected in parallel, as the reciprocal of the total resistance is the sum of the reciprocals of individual resistances.
Explain the concept of electrical power in a circuit.
Answer: Electrical power is the rate at which electrical energy is consumed or converted into other forms of energy in a circuit.
How does temperature affect the conductivity of semiconductors?
Answer: The conductivity of semiconductors increases with an increase in temperature, as more charge carriers are available.
What is the internal resistance of a cell, and how does it affect the output voltage?
Answer: Internal resistance is the resistance within the cell itself, which causes a drop in the output voltage when current flows.
Differentiate between electromotive force (emf) and terminal voltage of a cell.
Answer: Emf is the total energy provided by the cell per unit charge, while terminal voltage is the actual voltage across the terminals of the cell, which is emf minus the voltage drop due to internal resistance.
What is the role of a fuse in an electric circuit?
Answer: A fuse protects the circuit by breaking the connection when the current exceeds a safe level, preventing damage due to overheating or fire.
Explain how a potentiometer can be used to measure the emf of a cell.
Answer: A potentiometer measures the emf of a cell by balancing the unknown emf against a known potential difference without drawing current from the cell.
What is a Wheatstone bridge, and what is its principle?
Answer: A Wheatstone bridge is an electrical circuit used to measure an unknown resistance by balancing two legs of a bridge circuit.
Its principle is based on Kirchhoff’s laws.Discuss the significance of superconductivity.
Answer: Superconductivity is a phenomenon where a material exhibits zero resistance below a certain critical temperature, leading to the perfect conductance of electricity.
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