Complete Study Material for JEE, NEET, CBSE Board Class 11 Exams
Electricity is a crucial topic in physics, fundamental to various applications and essential for competitive exams like JEE, NEET, and CBSE Board Class 11. This guide covers key concepts, important formulas, multiple-choice questions (MCQs), conceptual questions, FAQs, worksheets, and test papers.
Physical Quantities, Units, and Dimensions Used in Electricity
| S. No | Quantity | Unit | Dimension |
|---|---|---|---|
| 1 | Electric charge (q) | Coulomb | [M⁰L⁰T¹A¹] |
| 2 | Electric current (I) | Ampere | [M⁰L⁰T⁰A¹] |
| 3 | Capacitance (C) | Farad | [M⁻¹L⁻²T⁴A²] |
| 4 | Electric potential (V) | Volt | [M¹L²T⁻³A⁻¹] |
| 5 | Permittivity of free space (ε₀) | Farad/meter | [M⁻¹L⁻³T⁴A²] |
| 6 | Dielectric constant (K) | Unitless | [M⁰L⁰T⁰] |
| 7 | Resistance (R) | Ohm | [M¹L²T⁻³A⁻²] |
| 8 | Resistivity (ρ) | Ohm-meter | [M¹L³T⁻³A⁻²] |
| 9 | Self-inductance (L) | Henry | [M¹L²T⁻²A⁻²] |
| 10 | Magnetic flux (φ) | Weber | [M¹L²T⁻²A⁻¹] |
| 11 | Magnetic induction (B) | Tesla | [M¹L⁰T⁻²A⁻¹] |
| 12 | Magnetic Intensity (H) | Ampere/meter | [M⁰L⁻¹T⁰A¹] |
| 13 | Magnetic Dipole Moment (M) | Ampere-meter² | [M⁰L²T⁰A¹] |
| 14 | Permeability of Free Space (μ₀) | Henry/meter | [M¹L¹T⁻²A⁻²] |
| 15 | Surface charge density (σ) | Coulomb/m² | [M⁰L⁻²T¹A¹] |
| 16 | Electric dipole moment (p) | Coulomb-meter | [M⁰L¹T¹A¹] |
| 17 | Conductance (G) (1/R) | Siemens | [M⁻¹L⁻²T³A²] |
| 18 | Conductivity (σ) (1/ρ) | Siemens/meter | [M⁻¹L⁻³T³A²] |
| 19 | Current density (J) | Ampere/m² | [M⁰L⁻²T⁰A¹] |
| 20 | Intensity of electric field (E) | Volt/meter | [M¹L¹T⁻³A⁻¹] |
| 21 | Rydberg constant (R) | m⁻¹ | [M⁰L⁻¹T⁰] |
Conceptual Questions with Answers
Q1: What is the significance of permittivity of free space (ε₀)?
A: Permittivity of free space determines how electric fields interact in a vacuum. It appears in Coulomb’s law and affects the strength of electrostatic forces.
Q2: Why is the unit of resistance in ohms (Ω)?
A: Resistance is the ratio of voltage to current (R = V/I), where voltage is in volts and current in amperes, leading to the derived unit ohm (Ω).
Q3: What is the physical meaning of capacitance?
A: Capacitance represents the ability of a system to store charge per unit voltage. It is measured in farads (F).
Multiple-Choice Questions (MCQs)
Q1: What is the SI unit of electric charge?
(a) Ampere
(b) Coulomb
(c) Volt
(d) Ohm
Answer: (b) Coulomb
Explanation: Electric charge is measured in coulombs (C), which represents the quantity of electricity transported by one ampere in one second.
Q2: The dimension of resistance is:
(a) [M¹L²T⁻³A⁻²]
(b) [M¹L²T⁻²A⁻²]
(c) [M⁰L⁰T¹A¹]
(d) [M⁰L⁰T⁰A¹]
Answer: (a) [M¹L²T⁻³A⁻²]
Explanation: Resistance (R) = Voltage (V) / Current (I), and using dimensional analysis, we derive [M¹L²T⁻³A⁻²].
Do You Know?
- Ohm’s Law: Voltage (V) = Current (I) × Resistance (R)
- Kirchhoff’s Laws:
- First Law (Junction Rule): ΣI (in) = ΣI (out)
- Second Law (Loop Rule): Σ Voltage drops = Σ Voltage gains
- The SI unit of capacitance is named after Michael Faraday.
Worksheet
Fill in the Blanks
- The SI unit of electric current is _______.
- The unit of magnetic flux is _______.
- Ohm’s Law states that V = ____ × R.
- The unit of resistivity is _______.
Short Answer Questions
- Define electrical resistance and its unit.
- Explain the significance of dielectric constant.
- What is the relation between electric field (E) and electric potential (V)?
Test Paper
Section A: Objective (1 mark each)
- What is the dimensional formula of electric charge?
- Define the unit of capacitance.
Section B: Short Answer (2 marks each)
- Derive the formula for electric potential in terms of work done.
- Differentiate between resistance and resistivity.
Section C: Long Answer (5 marks each)
- Explain Kirchhoff’s laws with suitable examples.
- Derive the formula for the energy stored in a capacitor.
Quick Revision Points
- Charge (q): Measured in coulombs (C)
- Current (I): Flow of charge per unit time, measured in amperes (A)
- Voltage (V): Potential difference between two points, measured in volts (V)
- Resistance (R): Opposition to current flow, measured in ohms (Ω)
- Capacitance (C): Ability to store charge, measured in farads (F)
Test Your Knowledge (Quiz)
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Written by: Neeraj Anand
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