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Suggestions · Missing points · Network Operating Systems
Q2. What is IP addressing (IP address)?
  • Missing: Common mistake
Q4. What is a Network Operating System (NOS)? Write its features.
  • Missing: Common mistake
Q6. What do you mean by input and output redirection in Linux? Explain.
  • Missing: Common mistake
Q8. What is VI editor? Explain its operating modes.
  • Missing: Common mistake
Q11. What do you mean by Cyber Law? Explain.
  • Missing: Common mistake
Quick facts · Network Operating Systems
Linux creator
Linus Torvalds (1991)
Kernel
Brain of Linux
File system
Hierarchical / tree structure
Linux licence
GNU General Public Licence
Default shell
Bash (Bourne Again Shell)
sh developed by
Stephen Bourne, 1977
Korn shell by
David Korn
stdin / stdout / stderr
0 / 1 / 2
Terminal shortcut
Ctrl + Alt + T
Vi editor
Visual Editor — 3 modes
Root directory
Single /
Config files
/etc
Log files
/var
Static routing
Non-adaptive
Dynamic routing
Adaptive
CorelDRAW file
.cdr
PL/SQL error
Exception
Direct-to-customer selling
B2C
One-minute recaps
Q1. What is Linux? What are its features?
  • 1991, Linus Torvalds
  • Kernel = brain of OS
  • GNU GPL = free & open source
  • Multi-user + high stability
  • Runs on old hardware
Q2. What is IP addressing (IP address)?
  • Numerical label for a device
  • Uses Internet Protocol
  • Always unique on the network
  • Needed by TCP/IP to route packets
Q3. What is Network Routing? Explain its Types.
  • Routing = path selection
  • Nodes + links, many possible paths
  • Chooses shortest path, lowers cost
  • Static = manual / non-adaptive
  • Dynamic = protocol-based / adaptive
Q4. What is a Network Operating System (NOS)? Write its features.
  • Connects autonomous computers
  • LAN / inter-network functions
  • Sharing + security + remote access
  • File, print, web, backup services
  • Examples: Linux, Unix, Novell NetWare
Q5. What is shell? Discuss the various types of shells.
  • Shell = interface to Linux
  • Two classes: CLI and GUI
  • Bash = default, extended sh
  • sh = Stephen Bourne, 1977
  • ksh = David Korn, merges all
Q6. What do you mean by input and output redirection in Linux? Explain.
  • Redirection changes input/output source
  • stdin = 0 = keyboard = <
  • stdout = 1 = screen = >
  • stderr = 2 = errors = 2>
  • Can read from / write to files
Q7. Explain some useful Linux shell commands.
  • Terminal: Ctrl+Alt+T
  • User: who, who am i
  • Directory: pwd, ls, mkdir, cd, rmdir
  • File: cat, cp, mv, rm, grep, find, chmod
  • Process: ps, kill, netstat, echo, cal
Q8. What is VI editor? Explain its operating modes.
  • Vi = Visual Editor
  • Command mode = default
  • Insert mode = i key
  • Replacement mode = r key
  • Esc returns to command mode
Q9. List and explain the most important File system of Linux.
  • Everything is a file
  • Single root /
  • Hierarchical / tree structure
  • Full path vs relative path
  • Devices as files: /dev/sda
Q10. List and explain the most important directories in the Linux File system.
  • FHS: single root /
  • boot, bin, dev, sbin
  • etc = configuration
  • lib, media, usr
  • var = logs, tmp = temporary
Q11. What do you mean by Cyber Law? Explain.
  • Legal framework for internet & digital tech
  • E-commerce and digital transactions
  • Intellectual property + privacy
  • Cybercrime: hacking, fraud, malware
  • Internet governance & jurisdiction
Portion 3 · Revision flow · Network Operating System Administration
Win NT
  1. 01Made by MS (1993)
  2. 02Workstation (for users) & Server (for business)
  3. 0332-bit
  4. 04NTFS
  5. 05Costly
  6. 06Prone to viruses
Linux vs Win
  1. 01Linux = Free, Open Source, highly secure, case-sensitive
  2. 02Win = Paid, Proprietary, virus-prone, case-insensitive
Network Maintenance
  1. 01Upgrading
  2. 02Repairing
  3. 03Backing up
  4. 04Securing routers/switches/lines
NSS (Network Security Specialist)
  1. 01Manages passwords
  2. 02Sets up firewalls
  3. 03Installs antiviruses
  4. 04Stops hackers
Disk Partition
  1. 01Slicing a new hard drive
  2. 02Into logical parts
  3. 03Stored in a partition table
  4. 04Before adding files
LVM (Logical Volume Management)
  1. 01Physical Volumes (PV)
  2. 02Volume Groups (VG)
  3. 03Logical Volumes (LV)
Swap Space
  1. 01RAM 100% full
  2. 02Emergency virtual memory
  3. 03Continue execution
Mount Point
  1. 01A folder/directory (like /boot)
  2. 02Filesystem grafted into the OS tree
  3. 03Device becomes usable
Shell Scripting
  1. 01Automating commands in a .sh file
  2. 02Fast to write
  3. 03Slow to execute
  4. 04One error can break it
Firewall
  1. 01The digital wall blocking hackers
  2. 02Hardware
  3. 03Software
  4. 04Cloud
  5. 05Uses Packet Filtering to check data packets
Suggestions · Missing points · Network Operating System Administration

Every question in this chapter has its Remember box, exam tip, common mistake and quick revision points. Nothing missing.

Quick facts · Network Operating System Administration
Windows NT
New Technology — Microsoft, 1993
NT products
NT Workstation + NT Server
Windows NT file system
NTFS
Windows NT architecture
32-bit
NT Workstation processors
RISC
Linux licensing
Free and open-source — no licensing
Linux file names
Case-sensitive
Windows file names
Case-insensitive
Firewall types
Software, Hardware, Cloud, Packet Filtering
First step for a new disk
Disk partitioning (slicing)
LVM
Logical Volume Management — PV → VG → LV
Swap space
Virtual memory when RAM is full
Mount point
Directory where a filesystem is grafted
Shell script extension
.sh
Top-level directory
/
Executable files
/bin
Admin account
root
NOS
Network Operating System
One-minute recaps
Q1. What is Windows NT? Explain its advantages and disadvantages.
  • Windows NT = New Technology, Microsoft, 1993
  • Two products: NT Workstation + NT Server
  • Advantages: multitasking, advanced GUI, remote login
  • Disadvantages: costly, virus prone, frequent rebooting
  • 32-bit, uses NTFS
Q2. What is the difference between Linux and Windows?
  • Linux = free + open source / Windows = commercial + closed source
  • Linux customizable / Windows not customizable
  • Linux no licence / Windows licence required
  • Linux runs months–years without reboot / Windows less reliable
  • Linux high security / Windows most vulnerable to viruses & malware
  • Linux installs apps offline / Windows needs internet
  • Linux case-sensitive / Windows case-insensitive
  • Linux ease of use improved dramatically / Windows user-friendly
Q3. What is a firewall? Explain its types.
  • Firewall = hardware or software network security device
  • Monitors incoming + outgoing traffic
  • Separates secure internal network from open internet
  • Types: Software, Hardware, Cloud, Packet Filtering
  • Appeared as Model Paper 2026 Q19
Q4. What is the role and responsibilities of a Network Security Specialist (NSS)?
  • Controls authorization of access to data (IDs / passwords)
  • Maintains LAN, WAN and server architecture
  • Safety measures + data recovery plans
  • Installs and upgrades security software
  • Firewalls, policies, breach investigation, training
Q5. What do you mean by disk partition?
  • Disk partitioning = disk slicing
  • Creates one or more regions on a hard disk
  • First step for a newly manufactured disk
  • Locations and sizes stored in a partition table
  • Each partition = distinct logical part to the OS
Q6. What is LVM? Explain.
  • LVM = Logical Volume Management
  • PV → VG → LV
  • Mount points and filesystems created on LVs
  • Storage management solution for administrators
Q7. What do you mean by swap space?
  • Used when RAM is fully utilized
  • Inactive pages moved to swap space
  • Held in virtual memory
  • Frees RAM for concurrent programs
Q8. What is a mount point in Linux?
  • Mount point = directory where filesystems are grafted into the tree
  • Makes the device accessible
  • Filesystem unusable until mounted
  • Examples: /boot, /media/cdrom
Q9. What do you mean by shell scripting? Explain its advantages and disadvantages.
  • Shell = program to interact with OS functions
  • Shell script = run a range of commands without typing each time
  • Saved with .sh extension
  • Advantages: same syntax, quick to write, interactive debugging
  • Disadvantages: costly errors, slow, not for complex tasks
Q10. What do you mean by Network Maintenance?
  • Regular + corrective measures for network equipment
  • Routers and switches
  • Troubleshooting, upgrading, monitoring
  • Securing, backups, legal compliance
  • Updating device configurations
Portion 3 · Revision flow · Desktop Publishing (Advanced)
CorelDraw
  1. 01Coral Corporation
  2. 02Vector graphics software
  3. 03CDR file format
  4. 04Logos, business cards, motifs, signs
CorelDraw vs Photoshop
  1. 01Vector vs Raster
  2. 02Coral vs Adobe
  3. 03CDR vs PSD/PSB
  4. 04Designers vs Photographers
Components
  1. 01Menu bar
  2. 02Property bar
  3. 03Toolbox
  4. 04Toolbar
  5. 05Drawing page
  6. 06Color palette
Pixel → PPI
  1. 01Pixel = picture element
  2. 02Smallest unit of display
  3. 03PPI = Pixels Per Inch
  4. 04Pixel density
Bitmap vs Vector
  1. 01Pixels vs Objects
  2. 02Large vs Small size
  3. 03Loses quality vs No loss
  4. 04.bmp vs .svg
Four tools
  1. 01Crop → clip
  2. 02Pick → select & transform
  3. 03Zoom → magnify
  4. 04Text → characters & boxes
Import flow
  1. 01File > Import
  2. 02Choose folder
  3. 03Choose format
  4. 04Click file name
  5. 05Import
Export flow
  1. 01File > Export
  2. 02Choose folder
  3. 03Save as type
  4. 04File name
  5. 05Checkbox
  6. 06Export
Saving
  1. 01File > Save → CDR (editable)
  2. 02File > Publish to PDF
  3. 03Preset: Prepress
  4. 04Save
Text types
  1. 01Artistic Text → short + effects
  2. 02Click & type
  3. 03Paragraph Text → long + formatting
  4. 04Drag frame & type
Suggestions · Missing points · Desktop Publishing (Advanced)

Every question in this chapter has its Remember box, exam tip, common mistake and quick revision points. Nothing missing.

Quick facts · Desktop Publishing (Advanced)
CorelDraw developer
Coral Corporation / Coral Incorporation
CorelDraw type
Vector based graphic designing software
CorelDraw extension
CDR
Initial release
1989
Photoshop developer
Adobe Incorporation
Photoshop formats
PSD or PSB
Photoshop type
Raster / pixel based
Pixel
Picture element — smallest unit of a display
PPI
Pixels Per Inch
Bitmap native format
.bmp
Vector native format
.svg
LOGO
Language of graphics - oriented
Ruler bar
Shows cursor location; sets margins
Status bar
Cursor movements / symbol properties
Property bar
Dynamic bar with property options
Page Navigator
Add and move between pages
Text types
Artistic Text and Paragraph Text
Flyout
Tool with a small triangle in the corner
One-minute recaps
Q1. What is CoralDraw?
  • Vector graphics software
  • Coral Corporation
  • Illustrations, layout, photo editing, typography
  • 3D, rotation, transformation, effects
  • Multiple layers & multiple pages
  • High quality logo designs
Q2. What is the difference between Photoshop and CoralDraw? Explain.
  • Vector (Corel) vs Pixel/Raster (Photoshop)
  • Coral Corporation vs Adobe Incorporation
  • C++ vs Pascal + C++
  • CDR vs PSD/PSB
  • Logos & business cards vs Special effects
  • Graphic designers vs Professional photographers
  • Popularity: Less vs More
Q3. Explain the components of CoralDraw?
  • Menu bar
  • Property bar
  • Toolbox
  • Toolbar
  • Drawing page
  • Color palette
Q4. What is the difference between Pixel and PPI?
  • Pixel = smallest unit of display
  • pix = picture, el = element
  • PPI = Pixels Per Inch
  • PPI = pixel density of image/screen
Q5. What is the difference between Bitmap Image and vector image?
  • Pixels vs Objects
  • Edit pixels vs Edit objects
  • Large vs Small file size
  • Loses quality vs No quality loss
  • Real vs Cartoon-like
  • .bmp vs .svg
  • .bmp/.dib/.jpeg/.gif/.tiff/.png vs .cgm/.svg/.eps/.xml
Q6. Explain Crop tool, Pick tool, Zoom tool and text tool?
  • Crop → clipping
  • Pick → select & transform
  • Zoom → magnifying glass
  • Text → characters, text boxes, tables
Q7. How can you insert and export file in CorelDraw? Explain
  • File > Import
  • All file formats option
  • Enter = centre, Drag = resize, Spacebar = original position
  • File > Export
  • Save as type
  • Export this page only / Selected only / Do not show filter dialog
Q8. How can save drawing or file in CoralDraw?
  • File > Save → CDR
  • File > Publish to PDF
  • PDF preset: Prepress
  • CDR is re-editable
Q9. How can you create a drawing in CorelDraw? Explain.
  • Start → All programs → CorelDRAW Graphics Suite
  • Get started → New document
  • File → New
  • Name textbox
  • File → Open for existing
Q10. How can you enter text in CorelDraw? Explain.
  • Artistic Text
  • Short lines + drop shadows
  • Click & type
  • Paragraph Text
  • Large bodies + formatting
  • Drag frame & type
Q11. Explain the importance of toolbox in CorelDraw?
  • All drawing & editing tools
  • Colors, patterns, fills
  • Small triangle → flyout
  • Flyout arrow
  • Logos, motifs, signs
Portion 3 · Revision flow · Electric Charges and Fields
Charge basics
  1. 01Scalar quantity
  2. 02Unit Coulomb
  3. 03Dimension [AT]
  4. 04Quantized q = ±ne
  5. 05Always conserved
Gold-leaf electroscope
  1. 01Charged body touches disc
  2. 02Charge flows down rod
  3. 03Both leaves get same charge
  4. 04Leaves repel → diverge
Coulomb's law chain
  1. 01F ∝ q₁q₂
  2. 02F ∝ 1/r²
  3. 03F = kq₁q₂/r²
  4. 04k = 1/4πε₀ = 9×10⁹
  5. 05Vector form F₁₂ = −F₂₁
Dielectric constant
  1. 01Force in air F₀
  2. 02Force in medium Fₘ
  3. 03K = F₀/Fₘ
  4. 04K = εₘ/ε₀
  5. 05Water K = 80
Electric field
  1. 01Source charge makes field
  2. 02Test charge feels force
  3. 03E = F/q₀
  4. 04Point charge E = kQ/r²
  5. 05Vector, unit NC⁻¹
Dipole formulas
  1. 01p = q × 2l
  2. 02Axial E = 2kp r/(r²−l²)²
  3. 03Short dipole axial = 2kp/r³
  4. 04Equatorial = kp/r³
  5. 05E_axial = 2E_eq
Torque cases
  1. 01τ = pE sin θ
  2. 02θ = 0° stable, τ = 0
  3. 03θ = 90° τ max = pE
  4. 04θ = 180° unstable, τ = 0
Gauss's theorem
  1. 01Draw Gaussian surface
  2. 02Flux = ∮E·dS
  3. 03θ = 0° on sphere
  4. 04E × 4πr² = q/ε₀
  5. 05Φ = q/ε₀
Gauss applications
  1. 01Line charge E = λ/2πε₀r
  2. 02Plane sheet E = σ/2ε₀
  3. 03Shell outside E = kq/r²
  4. 04Shell surface E = σ/ε₀
  5. 05Shell inside E = 0
Field line rules
  1. 01Start on +, end on −
  2. 02Never cross
  3. 03No closed loops
  4. 04⊥ to conductor surface
  5. 05Zero inside conductor
Suggestions · Missing points · Electric Charges and Fields

Every question in this chapter has its Remember box, exam tip, common mistake and quick revision points. Nothing missing.

Quick facts · Electric Charges and Fields
SI unit of charge
Coulomb (C)
Dimensional formula of charge
[AT]
Elementary charge e
1.6 × 10⁻¹⁹ C
Electrostatic constant k
9 × 10⁹ N m² C⁻²
Permittivity of free space ε₀
8.854 × 10⁻¹² C² N⁻¹ m⁻²
Dimensional formula of ε₀
[M⁻¹L⁻³T⁴A²]
K for water / air / vacuum
80 / 1.00059 / 1
E field unit
N C⁻¹, dimension [MLT⁻³A⁻¹]
Dipole moment
p = q × 2l, unit C m
Torque on dipole
τ = pE sin θ
Flux unit
N m² C⁻¹, dimension [ML³T⁻³A⁻¹]
1 Coulomb (CGS)
3 × 10⁹ statcoulomb (esu)
One-minute recaps
Q1. Explain the term electrostatics. Give some applications.
  • Study of charges at rest
  • Photocopier, capacitor, precipitator
  • Atomic structure, spray painting
Q2. What is an electric charge?
  • Causes electric force
  • Scalar
  • Coulomb (C)
  • [AT]
Q3. What is an electroscope? Discuss the working of a Gold-leaf Electroscope.
  • Detects presence and nature of charge
  • Disc → rod → gold leaf
  • Same charge = diverge more
  • Opposite charge = diverge less
Q4. Explain the methods of charging a material.
  • Conduction = touch and share
  • Friction = rubbing
  • Glass + silk, carpet, comb, hot iron
  • Induction excluded
Q5. Define conservation of electric charge.
  • Net charge of isolated system constant
  • Friction: +q − q = 0
  • Decay: 92 = 90 + 2
  • Pair production and annihilation: 0 = 0
Q6. Explain Quantization of Electric Charge.
  • q = ±ne
  • e = 1.6 × 10⁻¹⁹ C
  • n must be an integer
  • 1 C = 6.25 × 10¹⁸ electrons
Q7. Compare the properties of electric charge with that of the mass of a body.
  • Sign
  • Quantization
  • Conservation
  • Velocity dependence
  • Fundamental vs derived
Q8. Explain Coulomb's law.
  • F ∝ q₁q₂
  • F ∝ 1/r²
  • F = kq₁q₂/r²
  • k = 1/4πε₀
Q9. What is relative permittivity (Dielectric Constant)?
  • K = F₀/Fₘ
  • K = εₘ/ε₀
  • No unit
  • Water 80, metals ∞
Q10. What are the characteristics of Electrostatic force (Coulomb's force)?
  • Central
  • Spherically symmetric
  • Inverse square
  • Two-body
  • Conservative
Q11. Show vector form of Coulomb's law in accordance to Newton's 3rd law.
  • F₂₁ along r̂₁₂
  • r̂₁₂ = −r̂₂₁
  • F₁₂ = −F₂₁
  • Position vector form has |r|³
Q12. Define one Coulomb.
  • q₁ = q₂ = 1 C
  • r = 1 m
  • F = 9 × 10⁹ N
  • 1 C = 3 × 10⁹ esu
Q13. Compare electrostatic force and gravitational force.
  • Both long range, inverse square, central, conservative
  • Electrostatic: ± and medium dependent
  • Gravitational: always attractive, weakest
Q14. Show and explain Superposition Principle of electric charge.
  • Net force = vector sum
  • Each pair uses Coulomb's law
  • Summation form with |r₀ − rᵢ|³
Q15. What is meant by continuous charge distribution? Mention and explain different types of charge densities.
  • λ = q/L
  • σ = q/S
  • ρ = q/V
  • dq = λdl, σdS, ρdV
Q16. What do you understand by electric field? Define Electric field intensity.
  • Region of influence
  • E = F/q₀
  • Vector, NC⁻¹
  • Uniform vs non-uniform
Q17. Derive an expression for Electric field intensity due to a point charge at origin.
  • E = F/q₀
  • F = kQq₀/r²
  • E = kQ/r² r̂
  • E ∝ 1/r²
Q18. Define Electric field line. Explain its various properties.
  • Start +, end −
  • Tangent gives direction
  • Never cross
  • Density = strength
  • No closed loops
Q19. What is an electric dipole? Define dipole moment.
  • Two equal opposite charges
  • p = q × 2l
  • Vector, − to +
  • Unit Cm
Q20. Find the electric field intensity at a point on the axial line of a dipole.
  • E₊ at (r−l)
  • E₋ at (r+l)
  • Subtract
  • 4rl in numerator
  • Short dipole: 2kp/r³
Q21. Find electric field intensity at a point on the equatorial line (broad side position) of a dipole.
  • Distance √(r²+l²)
  • Sinθ cancels, cosθ adds
  • E = kp/(r²+l²)^{3/2}
  • Short dipole kp/r³
  • Opposite to p
Q22. Show that the torque experienced by an electric dipole is the cross product of dipole moment and electric field.
  • Couple of forces qE
  • Arm = 2l sinθ
  • τ = pE sinθ
  • τ = p × E
  • Max at 90°
Q23. What do you understand by area vector? What is electric flux?
  • dS⃗ = dS n̂ outward
  • dΦ = E dS cosθ
  • Φ = ∮E·dS
  • Unit Nm²C⁻¹
Q24. State Gauss's theorem and prove it.
  • Φ = q/ε₀
  • Spherical Gaussian surface
  • θ = 0°
  • ∮dS = 4πr²
  • E×4πr² = q/ε₀
Q25. Derive Coulomb's law from Gauss's theorem.
  • Gaussian sphere on q₁
  • E = kq₁/r²
  • F = q₂E
  • F = kq₁q₂/r²
Q26. Electric field at a point near an infinitely long uniformly charged wire (application of Gauss's theorem).
  • Cylindrical Gaussian surface
  • q = λl
  • Caps give zero flux
  • E(2πrl) = λl/ε₀
  • E = λ/2πε₀r
Q27. Electric field intensity due to a uniformly charged infinite plane sheet.
  • Cylinder through sheet
  • q = σA
  • Φ = 2EA
  • E = σ/2ε₀
  • Capacitor: σ/ε₀ inside, 0 outside
Q28. Electric field intensity due to a uniformly charged thin spherical shell.
  • Outside: kq/r²
  • Surface: σ/ε₀
  • Inside: 0
  • Graph peaks at r = R
Portion 3 · Revision flow · Electrostatic Potential and Capacitance
Potential basics
  1. 01Work per unit +ve charge
  2. 02From infinity
  3. 03V = W/q₀
  4. 04Scalar, unit volt
  5. 05Point charge V = kq/r
Dipole potential cases
  1. 01General V = p cos θ / 4πε₀r²
  2. 02Axial θ = 0° → p/4πε₀r²
  3. 03Equatorial θ = 90° → V = 0
  4. 04Dipole V ∝ 1/r²
E and V
  1. 01Move q₀ by dr against E
  2. 02dW = −q₀E dr
  3. 03dV = −E dr
  4. 04E = −dV/dr
  5. 05Field points to falling V
Equipotential properties
  1. 01W = 0 on surface
  2. 02E ⊥ surface
  3. 03Close surfaces = strong field
  4. 04Never intersect
Conductor rules
  1. 01E inside = 0
  2. 02E ⊥ surface outside
  3. 03Charge inside = 0
  4. 04Charge on outer surface
  5. 05V constant
Dielectric chain
  1. 01Apply E₀
  2. 02Polarization → Ep
  3. 03E = E₀ − Ep
  4. 04K = E₀/E
  5. 05K = 1 + χₑ
Capacitor formulas
  1. 01C = q/V
  2. 02Sphere C = 4πε₀r
  3. 03Plates C = Aε₀/d
  4. 04Dielectric slab C = Aε₀/(d − t + t/K)
  5. 05Conducting slab C = Aε₀/(d − t)
Slab cases
  1. 01t = d → KC₀
  2. 02t = d/2 → 2KC₀/(K+1)
  3. 03t = 2d/3 → 3KC₀/(K+2)
Series vs parallel
  1. 01Series: same q, V divides
  2. 021/Cs = 1/C₁ + 1/C₂ + …
  3. 03Parallel: same V, q divides
  4. 04Cp = C₁ + C₂ + …
Energy with dielectric
  1. 01U = ½CV² = Q²/2C
  2. 02Battery OFF: Q const → U₀/K
  3. 03Battery ON: V const → KU₀
  4. 04u = ½ε₀E²
Suggestions · Missing points · Electrostatic Potential and Capacitance
Q1. Define electric potential. Derive the expression for potential due to a point charge.
  • Missing: Common mistake
Q2. Define electric potential difference and one volt.
  • Missing: Exam tip
  • Missing: Common mistake
  • Missing: Quick revision points
Q3. Write the potential due to a system of point charges (superposition).
  • Missing: 🧠 Remember box
  • Missing: Exam tip
  • Missing: Quick revision points
Q4. Define electrostatic potential energy and electron volt.
  • Missing: 🧠 Remember box
  • Missing: Exam tip
  • Missing: Common mistake
  • Missing: Quick revision points
Q5. What is potential gradient?
  • Missing: 🧠 Remember box
  • Missing: Exam tip
  • Missing: Common mistake
  • Missing: Quick revision points
Q6. Differentiate between conductors, insulators and dielectrics. What are polar and non-polar dielectrics?
  • Missing: 🧠 Remember box
  • Missing: Exam tip
  • Missing: Common mistake
  • Missing: Quick revision points
Q7. Define capacitor, capacitance, permittivity and dielectric constant.
  • Missing: 🧠 Remember box
  • Missing: Exam tip
  • Missing: Common mistake
  • Missing: Quick revision points
Q8. Formula and units sheet — Chapter 2
  • Missing: 🧠 Remember box
  • Missing: Exam tip
  • Missing: Common mistake
  • Missing: Quick revision points
Q10. Compare electric potential due to an isolated charge and an electric dipole.
  • Missing: 🧠 Remember box
  • Missing: Exam tip
  • Missing: Common mistake
  • Missing: Quick revision points
Q11. Prove that electric field intensity is the negative potential gradient: E = −dV/dr.
  • Missing: Exam tip
  • Missing: Common mistake
Q12. What is an equipotential surface? Write its properties.
  • Missing: 🧠 Remember box
  • Missing: Common mistake
Q13. Derive the potential energy of a system of two and three point charges.
  • Missing: 🧠 Remember box
  • Missing: Exam tip
  • Missing: Common mistake
Q14. Explain the behaviour of conductors in an electric field. What is electrostatic shielding?
  • Missing: 🧠 Remember box
  • Missing: Exam tip
  • Missing: Common mistake
Q15. Explain dielectrics and polarization. Define dielectric constant, polarization vector, susceptibility and dielectric strength. Prove K = 1 + χₑ.
  • Missing: 🧠 Remember box
  • Missing: Exam tip
  • Missing: Common mistake
Q16. Define electrical capacitance. Find the capacitance of an isolated spherical conductor. Is a 1 F conductor possible?
  • Missing: Exam tip
  • Missing: Common mistake
  • Missing: Quick revision points
Q17. Parallel plate capacitor: principle, capacitance, with dielectric slab and with conducting slab.
  • Missing: 🧠 Remember box
Q18. Derive the equivalent capacitance for series and parallel combination of capacitors.
  • Missing: Exam tip
  • Missing: Common mistake
Q19. Derive the energy stored in a capacitor and energy density. Explain the effect of a dielectric on energy stored.
  • Missing: 🧠 Remember box
  • Missing: Exam tip
Quick facts · Electrostatic Potential and Capacitance
ε₀
8.854 × 10⁻¹² C² N⁻¹ m⁻²
1/4πε₀
9 × 10⁹ N m² C⁻²
1 eV
1.6 × 10⁻¹⁹ J
Unit of potential
Volt = J C⁻¹, [ML²T⁻³A⁻¹]
Unit of capacitance
Farad = C V⁻¹, [M⁻¹L⁻²T⁴A²]
1 µF / 1 nF / 1 pF
10⁻⁶ F / 10⁻⁹ F / 10⁻¹² F
Capacitance of Earth
≈ 711 µF
Energy density
u = ½ε₀E², J m⁻³
One-minute recaps
Q1. Define electric potential. Derive the expression for potential due to a point charge.
  • V = W/q₀
  • Scalar, volt
  • [ML²T⁻³A⁻¹]
  • Point charge V = kq/r
Q9. Electric potential due to an electric dipole — axial line, equatorial line and any point.
  • V_axial = p/4πε₀(r² − l²)
  • Short dipole → p/4πε₀r²
  • V_equatorial = 0
  • V = p cos θ/4πε₀r²
Q11. Prove that electric field intensity is the negative potential gradient: E = −dV/dr.
  • dW = −q₀E dr
  • dV = dW/q₀
  • E = −dV/dr
Q12. What is an equipotential surface? Write its properties.
  • W = 0
  • E ⊥ surface
  • Closer = stronger field
  • Never intersect
Q13. Derive the potential energy of a system of two and three point charges.
  • U(2) = kq₁q₂/r₁₂
  • U(3) = k[q₁q₂/r₁₂ + q₁q₃/r₁₃ + q₂q₃/r₂₃]
  • 1 J = 1 C V
Q14. Explain the behaviour of conductors in an electric field. What is electrostatic shielding?
  • E inside = 0
  • E ⊥ surface
  • q inside = 0
  • Charge on outer surface
  • V constant
  • Shielding: car in lightning
Q15. Explain dielectrics and polarization. Define dielectric constant, polarization vector, susceptibility and dielectric strength. Prove K = 1 + χₑ.
  • E = E₀ − Ep
  • K = E₀/E > 1
  • P = np = σp
  • P = χₑε₀E
  • K = 1 + χₑ
Q17. Parallel plate capacitor: principle, capacitance, with dielectric slab and with conducting slab.
  • C = Aε₀/d
  • Dielectric: C = Aε₀/(d − t + t/K)
  • t = d → KC₀
  • Conducting slab: C = Aε₀/(d − t)
Q18. Derive the equivalent capacitance for series and parallel combination of capacitors.
  • Series: same q, 1/Cs = Σ1/C
  • Parallel: same V, Cp = ΣC
  • Cp > largest C, Cs < smallest C
Q19. Derive the energy stored in a capacitor and energy density. Explain the effect of a dielectric on energy stored.
  • U = Q²/2C = ½CV² = ½QV
  • u = ½ε₀E²
  • Battery off → U₀/K
  • Battery on → KU₀