Misconceptions — Common Wrong Beliefs Corrected — Notes | NoteTube

✗ Wrong Belief	✓ Correct Statement	Explanation
"Magnetic force does work on charged particles"	Magnetic force does NO work on moving charges	F = qv×B is always ⊥ to v; work = F· $\Delta r$ = 0 since F ⊥ displacement
"Time period decreases when particle moves faster in magnetic field"	T = 2π $\frac{m}{qB}$ is completely independent of velocity	Faster particle → larger radius → longer path; these effects cancel exactly
"Inside a toroid, there is no field anywhere"	B = 0 in hollow centre AND outside; B = μ_{0} $\frac{NI}{2πr}$ inside the ring material	The field is confined to the region within the toroid windings only
"Diamagnetic materials have no response to magnetic fields"	Diamagnetic materials are REPELLED (weakly) by external fields	χ < 0 means magnetisation is opposite to field; material moves to weaker field regions
"Connecting a large resistance in parallel makes a voltmeter"	A voltmeter requires large resistance in SERIES	Parallel connection would create a low-resistance branch; voltmeter needs series R to limit current
"The solenoid field depends on total number of turns N"	B = μ_{0}nI where n = $\frac{N}{L}$ ; total turns alone don't determine B	If you double solenoid length keeping N same, n halves, so B halves
"Magnetic field lines can start and end like electric field lines"	Magnetic field lines are always closed loops	No magnetic monopoles exist; ∮B·dA = 0 (Gauss's law for magnetism)
"Retentivity and coercivity are properties of all magnetic materials"	Only ferromagnets show hysteresis, retentivity, and coercivity	Dia and paramagnetic materials don't retain magnetism; hysteresis is a ferromagnetic phenomenon
"A current loop is equivalent to a bar magnet only when it has many turns"	Even a single-turn loop (N=1) acts as a magnetic dipole	M = NIA; for N=1, M = IA; the dipole behaviour doesn't require multiple turns
"Curie's law χ = $\frac{C}{T}$ applies to ferromagnets"	Curie's law applies only to PARAMAGNETS	Ferromagnets obey Curie-Weiss law χ = $\frac{C}{T − T_C}$ ; above Curie temp they become paramagnetic