Mnemonics: Class 12th Physics | Physics Class 12 - NEET PDF Download

Welcome to your ultimate guide for mastering Class 12 Physics through mnemonics! This EduRev document is packed with creative and easy-to-remember phrases that simplify complex formulas and concepts. From Electric Power to Hydrogen Spectra, these memory aids will make your learning journey both effective and enjoyable.

 Let’s dive in and decode the wonders of Physics effortlessly!

1. Electric Power

Mnemonic: "Power Plays with Three Friends: Voltage, Current, Resistance."

• Power Plays → Focus on Power (P)

Power is the rate at which energy is consumed or produced in an electrical circuit. It is measured in watts (W), it depends on voltage, current, and resistance.

• Three Friends → Voltage (V), Current (I), and Resistance (R)

These three quantities are interconnected and govern how power is calculated in various scenarios.

This mnemonic helps in understanding the relationship between power, voltage, current, and resistance and frequently used in problems involving electrical circuits and power dissipation.

2. Motional EMF

Mnemonic: "Move, Length, Field: EMF Revealed."

• Move → Motion of a conductor

Motion of a conductor is essential for generating motional EMF. The conductor must move with a velocity (v) relative to a magnetic field.

•  Length → Length of the Conductor (l)

The length of the conductor (l) perpendicular to the magnetic field directly affects the magnitude of the EMF induced. Longer conductors experience higher induced EMF.

•  Field → Magnetic Field (B)

The strength of the magnetic field (B) plays a crucial role.A stronger magnetic field induces a greater EMF.

• EMF Revealed → 

When these three factors—motion, length, and field strength—combine, they "reveal" the induced EMF in the conductor.

This mnemonic is primarily helpful in topics related to Electromagnetic Induction, which is a core concept in Class 12 Physics.

3. Alternating Current

Mnemonic: "Capacitors Love Current, Inductors Love Voltage, Resistors Love Balance."

• Capacitors Love Current → Current leads Voltage by + 90°.
• Inductors Love Voltage → Voltage leads Current by +90° .
• Resistors Love Balance →  Voltage and Current are in phase (0°).

Mnemonic Explanation:

• In a capacitive AC circuit:  Capacitors resist changes in voltage, charging and discharging quickly in response to AC signals. As a result, current flows ahead of the voltage.
• In an inductive AC circuit:  Inductors resist changes in current due to self-induction, producing a back electromotive force (EMF) that delays the current flow.
• In a resistive AC circuit: The voltage and current are in phase, meaning they rise and fall together with no time lag (0°phase difference). A resistor does not store energy but dissipates it as heat, which results in perfect synchrony between voltage and current.

The mnemonic "Capacitors Love Current, Inductors Love Voltage, Resistors Love Balance" provides a simple yet effective way to understand the behavior of AC circuits as described in the NCERT textbook. It is particularly helpful for:

• Learning phase differences in AC circuits.
• Understanding LCR circuits and impedance.
• Solving numerical problems efficiently.
• Preparing for practical exams and competitive exams like NEET and JEE.

4. Electromagnetic Spectrum

Mnemonic:"Ravi’s Mother Invites Very Ugly X-rated Guests."

•  Ravi’s → Radio Waves ( Longest wavelength and lowest frequency).
•  Mother→ Microwaves ( Slightly shorter wavelength than radio waves).
• Invites → Infrared ( Wavelength shorter than microwaves).
•  Very→ Visible Light ( The only part of the spectrum visible to the human eye).
• Ugly → Ultraviolet ( Higher frequency than visible light).
•  X-rated → X-rays ( High frequency and penetrating power).
•  Guests → Gamma Rays ( Highest frequency and shortest wavelength).

Order of Spectrum

The decreasing order of wavelength of the Electromagnetic Spectrum (from Radio Waves to Gamma Rays) is a stepping stone for mastering:

• Foundation of understanding how energy, frequency, and wavelength vary in different waves.
• Understanding the order simplifies solving numerical problems related to wavelength, frequency, and energy.

5. Einstein's Equation of Photoelectric Effect

Mnemonic: "WE Unite to form People"

Energy of emitted electron + Work function = Energy of incident photon

Interpretation:

$\mathrm{<br\; style="box-sizing:\; border-box;\; font-family:\; Lato,\; sans-serif;\; letter-spacing:\; inherit;\; word-break:\; break-word;\; font-size:\; 20px;\; color:\; black;\; line-height:\; 1.8;">}$E+ ϕ = hf

Or,

E = hf − ϕ

6. Ionisation Energy of Hydrogen

Mnemonic: "Thirteen Point Six Frees the Electron."

• Ionisation energy of hydrogen from the ground state: 13.6 eV.

This mnemonic simplifies the understanding of the ionisation energy of hydrogen, which is a key concept in atomic physics and quantum mechanics, covered in NCERT Class 12 Physics