Magnetism and Matter — Class 12 CBSE Physics revision notes
A 6-page visual revision sheet for Magnetism and Matter, 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
Magnetism and Matter in one look
a bar magnet is a current loop that never lost its current
The bar magnet and its field lines
- outside the magnet the lines run N to S, inside they run S to N
- so every line is a closed loop, none starts or ends
- the tangent to a line is the direction of B there
- lines crowd together where the field is strong: near the poles
- two lines never cross
- iron filings and a compass both trace the lines
A bar magnet is a solenoid
- its field matches a solenoid's, loop for loop
- magnetic moment m: points S to N, m = nIA for n turns
- a loop is a dipole: its N face is where the current runs anticlockwise
- the atoms' own circulating charges are the tiny loops inside the bar
Cut it: no lone pole
- cut a magnet in two and you get two magnets, never two lone poles
- an isolated N or S pole has never been found
- every piece keeps its own N and S, in the same order
- poles are a picture, the real source is the moving charge
The far field of a bar magnet
- on the axis (r far greater than the length)
B_axis = μ_0/4π2m/r^3 - on the equator (same r)
B_eq = μ_0/4pim/r^3 - the two compared
B_axis = 2B_eq
Page 1 of 6. The full sheet, all 6 pages, opens free in the app.
What this Magnetism and Matter sheet covers
- The bar magnet and its field lines
- A bar magnet is a solenoid
- Cut it: no lone pole
- The far field of a bar magnet
- on the axis (r far greater than the length)
- on the equator (same r)
- the two compared
- A magnet in a uniform field
- torque, as a vector
- torque, size
- potential energy
- Special angles
- Swinging about B
- The energy well
- Gauss's law for magnetism
- flux through ANY closed surface
- Gauss's law, magnetic against electric
- Magnetic
- Electric
- The three, side by side
- Diamagnetic
- Paramagnetic
- Ferromagnetic
- Susceptibility and permeability
- B in terms of H and M
- magnetic susceptibility
- relative permeability
- Curie's law, paramagnetic materials
- Domains and hysteresis
- Choosing a ferromagnet
- Soft iron
- Steel
- Earth's magnetism
- Three elements of the Earth's field
- Resolving the Earth's field
- horizontal component
- vertical component
- back to the total
- the dip from the two
- Symbols
- 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 Magnetism and Matter 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.