Q1: Explain the concept of electric current and its flow in a closed circuit. Describe the role of electric charges in the formation of an electric current.
Ans: Electric current is the flow of electric charges through a conductor. It occurs when there is a potential difference (voltage) across a closed circuit. The flow of electric charges is driven by the presence of free electrons within the conductor.
Formation of Electric Current:
Role of Electric Charges:
Q2: Explain Ohm's law and its mathematical representation. Describe the relationship between voltage, current, and resistance in an electrical circuit.
Ans: Ohm's law states that the current passing through a conductor is directly proportional to the voltage applied across it, provided its temperature remains constant. Mathematically, Ohm's law is represented as:
V = I . R
Where:
Relationship between Voltage, Current, and Resistance:
Ohm's law provides a fundamental relationship in electricity and helps in understanding how changes in voltage, current, and resistance affect each other in an electrical circuit.
Q3: Describe the construction and working of an electric circuit with the help of a schematic diagram. Explain the role of a switch, connecting wires, and components such as resistors in the circuit.
Ans: An electric circuit is a closed pathway through which electric current flows. It consists of various components interconnected by conductive wires. Let's consider a simple circuit with a switch, a resistor, and a power source (battery).
The construction and working of the circuit are as follows:
Role of Components:
In summary, an electric circuit consists of interconnected components and conductive wires, with the flow of electric current controlled by switches. Components like resistors introduce resistance and regulate current flow in the circuit.
Q4: Describe the concept of electric potential difference (voltage) in an electric circuit. Explain how the voltage across a resistor affects the current flowing through it.
Ans: Electric potential difference, also known as voltage, is the driving force that pushes electric charges to move in a circuit. It represents the energy transferred per unit charge as charges flow from a higher potential to a lower potential. Voltage is measured in volts (V).
Effect of Voltage on Current through a Resistor:
Q5: Explain the term "electric power" in an electrical circuit. Describe the relationship between electric power, current, and voltage. Provide the mathematical formula for calculating electric power.
Ans: Electric power is the rate at which electric energy is converted into other forms of energy, such as heat, light, or mechanical work, in an electrical circuit. It is measured in watts (W).
Relationship between Electric Power, Current, and Voltage:
Q6: Describe the working principle of an electric fuse and its role in electrical safety. Explain how a fuse prevents excessive current flow in a circuit.
Ans: An electric fuse is a safety device designed to protect electrical circuits and appliances from damage due to excessive current flow. It contains a thin wire that melts when subjected to high current, breaking the circuit and stopping the flow of electricity.
Working Principle and Role in Electrical Safety:
Importance of Fuses in Electrical Safety:
Q7: Explain the concept of electric resistance and its factors. Describe how the length, crosssectional area, and material of a conductor affect its resistance.
Ans: Electric resistance (R) is the opposition offered by a material to the flow of electric current. It depends on the material's properties, length (l), crosssectional area (A) of the conductor, and temperature.
Factors Affecting Electric Resistance:
Mathematical Relationship:
The resistance (R) of a conductor can be calculated using the formula:
R = ρ⋅l/A
Where:
In summary, resistance depends on the length, crosssectional area, and material of a conductor. Longer conductors with smaller crosssectional areas and materials with higher resistivities result in greater resistance.
Q8: Explain the working of an electric bell with the help of a circuit diagram. Describe the role of the electromagnet, armature, and contact points in the operation of the electric bell.
Ans: An electric bell is a simple device that converts electrical energy into mechanical motion and sound. It operates through the interaction of an electromagnet, an armature, and contact points.
The working of an electric bell is as follows:
Working Principle:
Role of Components:
Q9: Describe the difference between direct current (DC) and alternating current (AC) in an electrical circuit. Explain the generation and distribution of AC using the example of a power station and household appliances.
Ans: Direct Current (DC) and Alternating Current (AC) are two types of electric currents with distinct characteristics.
Difference between DC and AC:
Generation and Distribution of AC:
In summary, AC is generated, transmitted, and distributed for various applications, including powering household appliances, due to its ability to be easily transformed and transmitted over long distances with minimal energy loss.
Q10: (a) List the factors on which the resistance of a conductor depends.
(b) A 4 kW heater is connected to a 220 V source of power. Calculate
(i) the electric current passing through the heater.
(ii) the resistance of the heater.
(iii) the electric energy consumed in 2 hour use of the heater.
Ans: (a) Resistance of a conductor depends on
(i) length of conductor (l)
(ii) Area of crosssection (A)
(iii) Resistivity of material (ρ)
Relation of resistance is given by,
(b) Given, P = 4 kW = 4000 W and V = 220 V
(i) P = VI or I = P/A
Hence, I = 4000/220 = 18.18 A
(ii) V = IR or R = V/I
R = 220/18.18 = 12.1Ω
(iii) Energy consumed, E = P × t
E = 4000 W × 2h = 8000Wh = 8 kWh = 8 unit.
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1. What is electricity and how is it generated? 
2. What is the role of conductors and insulators in electrical circuits? 
3. What are the different units used to measure electricity? 
4. What are the safety precautions to be followed while dealing with electricity? 
5. How can electricity be used efficiently and sustainably in everyday life? 

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