CBSE Class 12 Physics Magnetic Effects Of Current And Magnetism Concept Map

This Class 12 Physics concept map covers magnetism, bar magnets and the solenoid, the Earth's magnetic elements, the magnetic effects of current (Lorentz force, Biot-Savart law, Ampere's circuital law and Ampere's force), the A.C. circuits (resistive, inductive, capacitive and LCR series circuits) and the photoelectric effect.

CONCEPT MAP: MAGNETIC EFFECT OF CURRENT AND MAGNETISM

MAGNETISM

Barmagnet
Barmagnet → Mag. field intensity
Barmagnet → Mag. field lines
Barmagnet → Magnetic substances → Diamagnetic, Paramagnetic, Ferro-magnetic
Ferro-magnetic → Strong ferro POINT (permanent magnet)
Ferro-magnetic → Soft ferro (electro magnet)

Solenoid as a bar magnet

Earth's magnet
Earth's magnet → Angle of declination
Earth's magnet → Horizontal component

Earth's magnetic elements
Earth's magnetic elements → Angle of dip → Axial point and Equatorial

[Figure: Concept map. Magnetism at the top, with three branches: Barmagnet, Solenoid as a bar magnet and Earth's magnet]

MAGNETIC EFFECT OF CURRENT

Lorentz force law
Lorentz force law → Velocity selector
Lorentz force law → Cyclotron
Lorentz force law → M.C.G (moving coil galvanometer)

Biot Savart
Biot Savart → Straight long current conductor
Biot Savart → Current circular loop

Ampere circuital
Ampere circuital → Solenoid/toroid
Ampere circuital → Hollow/solid long current conductor

Ampere force
Ampere force → Torque on the current loop → Ammeter and Voltmeter

A.C. CIRCUITS

[Figure: Concept map with A.C. Circuits at the top and four branches: Purely resistive circuit, Purely inductive circuit, Purely capacitive circuit and L C R series circuit. A box for each of the first three says In absence of L and C, In absence of R and C, and In absence of R and L respectively, and the bottom bar joins these to Resonance]

Purely resistive circuit
Z = R
Φ = 0
CosΦ = 1
e = e₀ sin ωt
i = i₀ sin ωt

Purely inductive circuit
Z = Lω
Φ = \( \frac{\pi}{2} \)
CosΦ = 0
e = e₀ sin ωt
i = i₀ sin(ωt - \( \frac{\pi}{2} \))

Purely capacitive circuit
Z = \( \frac{1}{\omega C} \)
Φ = \( \frac{\pi}{2} \)
CosΦ = 0
e = e₀ sin ωt
i = i₀ sin(ωt + \( \frac{\pi}{2} \))

L C R series circuit
Z = \( \sqrt{R^2 + \left(L\omega - \frac{1}{C\omega}\right)^2} \)
Φ = \( \tan^{-1} \frac{L\omega - \frac{1}{C\omega}}{R} \)
CosΦ = \( \frac{R}{Z} \)
e = e₀ sin ωt
i = i₀ sin(ωt - φ)

Resonance: Lω = \( \frac{1}{C\omega} \)

PHOTOELECTRIC EFFECT

Photon (energy = hν) is incident on a photosensitive material, which has a work function φ₀.

Case 1: hν < φ₀
No emission → Photoelectric current I_p = 0

Case 2: hν = φ₀
Emission occurs → No kinetic energy → Photoelectric current I_p = 0

Case 3: hν > φ₀
Emission occurs → Maximum kinetic energy depends on frequency → \( \frac{1}{2} mv^2 \) → Photoelectric current (the label is cut off in the source)

Collector potential
Collector potential → -ve → I_p decreases, and at V = V_cutoff the photoelectric current becomes zero
Collector potential → +ve → Photoelectric current (the label is cut off in the source)

[Figure: Concept map of the photoelectric effect. Photon (Energy = hν) incident on a Photosensitive material (Work function = φ₀). Three cases: hν < φ₀, hν = φ₀ and hν > φ₀, each leading to emission or no emission, and to the collector potential with -ve and +ve branches]