Electromagnetic Induction — Class 12 CBSE Physics revision notes
A 6-page visual revision sheet for Electromagnetic Induction, written for Class 12 CBSE Physics. Formulas, diagrams and the traps that cost marks, laid out to be read the night before rather than the term before. Free, and it opens inside CapCompass.
Page 1 as PDF
Electromagnetic Induction in one look
a changing flux is the only thing that ever induces an emf
Faraday's and Henry's experiments
- a magnet moved toward a coil: the galvanometer kicks only while it moves; faster, bigger
- pulled away, the kick reverses; held still, no current at all
- a current-carrying coil carried in acts just like the magnet
- both coils still: switching coil 1 on or off kicks; a steady current induces nothing
- an iron rod through the coils makes the kick much bigger
- the common cause: the magnetic flux through the coil is changing
Magnetic flux
- uniform B through a flat area A
Φ_B = BAcosθ - θ: between B and the area's normal
Φ_B = BcdotA - curved surface, non-uniform B
Φ_B = sumB· dA - SI unit, the weber
1 Wb = 1 T m^2
Faraday's law of induction
- one loop
ε = -dΦ_B/dt - N turns, each linking Φ
ε = -NdΦ_B/dt
Page 1 of 6. The full sheet, all 6 pages, opens free in the app.
What this Electromagnetic Induction sheet covers
- Faraday's and Henry's experiments
- Magnetic flux
- uniform B through a flat area A
- θ: between B and the area's normal
- curved surface, non-uniform B
- SI unit, the weber
- Faraday's law of induction
- one loop
- N turns, each linking Φ
- Three ways to change the flux
- Lenz's law and conservation of energy
- Motional emf
- rod of length l at speed v across B, all at right angles
- from the flux it encloses, or the force on each charge
- current, and the field's force on the rod against v
- your power equals the heat
- let go on flat rails: it brakes itself
- upright rails: it falls to a terminal speed
- Motional emf in a rotating rod
- a bit dr at radius r moves at ωr
- rod of length l about one end
- Eddy currents
- Eddy currents at work
- Mutual inductance
- coil 2's flux linkage from I_1
- emf induced in coil 2
- either way round
- coil 1, radius r_1, inside coil 2
- What sets M
- Self-inductance
- flux linkage from its own current
- the back emf
- long solenoid
- with an iron core
- Energy stored in an inductor
- work against the back emf
- energy per volume of field
- Limits of self-inductance
- Switching on and switching off
- Switching on
- Switching off
- AC generator
- N turns turning at ω in B
- the emf
- its peak
- Traps that cost marks
- Tricks that save time
How CapCompass uses this sheet
These notes are not a standalone PDF. CapCompass plans Physics chapter by chapter against your real exam dates and free hours, and when the plan reaches Electromagnetic Induction the sheet opens inside the study block itself — at the page covering the sub-topic that block is on, with the timer still running. Revision arrives at the moment the plan says revise, instead of having to be gone looking for.