Important Questions on Current Electricity with Solutions
Current Electricity Practice Paper for Students
FAQs on Current Electricity Practice Paper for Students
1. What is current electricity?
Current electricity refers to the flow of electric charge through a conductor, usually measured in amperes (A).
- It arises due to the motion of electrons in a material.
- The direction of current is taken as the direction of positive charge flow, opposite to electron motion.
- Current electricity is a major topic for CBSE exams under Physics Class 12, including concepts like Ohm’s law, resistivity, and electrical circuits.
2. State Ohm's law and its mathematical expression.
Ohm’s law explains the relationship between voltage, current, and resistance in an electrical circuit.
- Summary: The current passing through a conductor between two points is directly proportional to the voltage across the two points at constant temperature.
- Mathematical Expression: V = IR
- Where V is voltage (volts), I is current (amperes), and R is resistance (ohms).
3. What are the differences between conductors and insulators?
Conductors allow the easy flow of electric current, while insulators prevent it.
- Conductors (e.g., copper, silver):
• Have free electrons
• Low resistance
- Insulators (e.g., rubber, plastic):
• Do not have free electrons
• High resistance
This distinction is essential for exam concepts and practical applications in circuits.
4. What factors affect the resistance of a conductor?
The resistance of a conductor depends on several physical properties:
- Length (R ∝ l): Resistance increases with length.
- Area (R ∝ 1/A): Resistance decreases with thicker wires.
- Resistivity (ρ): Material property (e.g., copper is low, nichrome is high).
- Temperature: For metals, resistance increases with temperature.
Understanding these factors helps in solving circuit problems and designing safe electrical systems.
5. Explain the concept of electric current and its SI unit.
Electric current is the rate of flow of electric charge through a conductor.
- SI unit: Ampere (A)
- Formula: I = Q/t, where Q is charge in coulombs and t is time in seconds.
- Common in circuits, current indicates how many charges flow in a given time, which is a key exam concept in current electricity.
6. What is meant by resistivity of a material?
Resistivity is an intrinsic property of a material that quantifies how strongly it resists current flow.
- Symbol: ρ (rho)
- Unit: ohm-meter (Ω·m)
- Depends only on the nature of the material and temperature.
- Used in the formula R = ρl/A, vital for CBSE numerical questions.
7. What are the applications of Ohm's law in daily life?
Ohm’s law is applied wherever electrical circuits exist.
- Used to determine values of current, voltage, or resistance in:
• Household wiring
• Electric appliances
• Troubleshooting circuit faults
- Central to designing safe and functional electric circuits for CBSE practicals and everyday use.
8. Explain the difference between series and parallel circuit connections.
Series and parallel circuits connect resistors differently, affecting current and voltage.
- In series:
• Current is same through all resistors
• Total resistance is sum of individual resistances
- In parallel:
• Voltage is same across all branches
• Total resistance is less than the smallest branch
Understanding these differences is important for solving circuit problems in exams.
9. How is electric power calculated in a circuit?
Electric power is the rate at which electrical energy is consumed.
- Formula: P = VI, where V is voltage and I is current
- Alternative forms:
• P = I^2R
• P = V^2/R
- SI unit: Watt (W)
This calculation is frequently tested in CBSE Physics numericals for current electricity.
10. What happens to the resistance of a metal wire as temperature increases?
As temperature increases, the resistance of a metal wire generally increases.
- This is due to increased vibration of metal atoms, which scatters electrons.
- The relationship can be described by: R = R₀[1 + α(T – T₀)]
- This concept appears in both theory and numericals on resistance and temperature in exams.






















