Don't Lose Marks on These Class 10 Physics Numericals

Video Overview Duration: ~25 minutes 38 seconds Subject/Context: Class 10 Science (Physics) — Section C Previous Year Exam Questions walkthrough, covering optics, electricity, and electromagnetism. Key Topics & Problem Breakdown 1. Human Eye & Power of Accommodation (00:00 – 03:31) Question: What happens to the eye lens and ciliary muscles when viewing an object close to the eye? Core Concepts Covered: Least distance of distinct vision ($25\text{ cm}$) vs. infinite vision. Action of ciliary muscles (contracting vs. relaxing) and changes in eye lens curvature/thickness. Definition and exam-oriented points for the Power of Accommodation. 2. Convex Lens Formula & Magnification (03:32 – 07:08) Question: Convex lens with focal length $f = +15\text{ cm}$ forming a real, same-sized image ($m = -1$). Finding object distance ($u$) and image distance ($v$). Core Concepts Covered: Cartesian sign conventions for convex lenses. Magnification formula ($m = \frac{v}{u}$). Solving using the lens formula: $\frac{1}{v} - \frac{1}{u} = \frac{1}{f}$, obtaining $v = +30\text{ cm}$ and $u = -30\text{ cm}$. 3. Prism Dispersion vs. Atmospheric Scattering (07:09 – 11:30) Question: Assertion-Reason problem on white light passing through a glass prism producing a 7-color spectrum. Core Concepts Covered: Refraction and dispersion through a triangular prism (VIBGYOR). Why scattering of light does not cause the rainbow spectrum in a prism. Relationship between wavelength ($\lambda$), speed of light in glass, and angle of deviation (violet bends most, red bends least). 4. Electric Resistance & Resistivity (11:31 – 12:57) Question: Calculating resistivity ($\rho$) given conductor resistance ($7,\Omega$), length, and circular cross-section radius. Core Concepts Covered: Formula: $R = \rho \frac{L}{A}$, where $A = \pi r^2$. Step-by-step substitution and units ($\Omega\cdot\text{m}$). 5. Electric Heater Power Consumption (12:58 – 15:57) Question: An electric heater rated at $220\text{ V}$ and $11\text{ A}$; calculating power consumed when operated at a reduced voltage ($200\text{ V}$). Core Concepts Covered: Finding internal resistance from rated values ($R = \frac{V}{I} = 20,\Omega$). Calculating actual operating power using $P = \frac{V^2}{R}$. 6. Convex Mirror Image Formation (15:58 – 17:22) Question: Identifying the mirror that always produces a virtual, erect, and diminished image. Core Concepts Covered: Convex mirror characteristics. Ray diagram setup showing an object anywhere between infinity and the pole. 7. Force on a Current-Carrying Conductor & Fleming’s Left-Hand Rule (17:23 – 25:38) Activity Demonstration: Aluminium rod suspended in a magnetic field between the poles of a horseshoe magnet. Chamber Problem: An electron beam traveling from back wall to front wall deflected to the right; determining magnetic field direction (vertically downward) using conventional current direction and Fleming's Left-Hand Rule.