Physics
About 6 min · General Awareness · English
Time worked out from the lesson's 403 words at 150 words a minute, plus a minute for each question.
The exam tests basic conceptual understanding rather than numerical problem-solving. Questions are fact-based and focus on everyday applications of physical principles—how devices work, units of measurement, laws and their discoverers, and fundamental phenomena.
Key ideas
- Force and Motion: Newton's three laws govern all motion. First law (inertia), second law (F = ma), third law (action-reaction). Understand friction as a force opposing motion and gravity as the force attracting objects toward Earth.
- Energy Forms: Energy cannot be created or destroyed, only converted (Law of Conservation of Energy). Kinetic energy is energy of motion; potential energy is stored energy. Work is force applied over distance.
- Current Electricity: Electric current is flow of electrons. Conductors allow flow (copper, silver); insulators resist it (rubber, plastic). Ohm's Law (V = IR) relates voltage, current, and resistance.
- Light Behavior: Light travels in straight lines, reflects off surfaces, and refracts (bends) when entering different media. Mirrors form images by reflection; lenses by refraction. Dispersion splits white light into colors.
- Atomic Structure: Atoms consist of protons (positive), neutrons (neutral), and electrons (negative). Radioactivity is spontaneous emission of particles/energy from unstable nuclei.
Watch out for
- Mass vs Weight Confusion: Mass is the amount of matter (constant everywhere, measured in kg). Weight is gravitational force on mass (varies with location, measured in newtons). On Moon, your mass stays same but weight reduces to 1/6th.
- Heat vs Temperature: Temperature measures average kinetic energy of molecules (degree of hotness). Heat is total thermal energy transferred between objects. A cup of boiling water has higher temperature than a bucket of warm water, but the bucket contains more heat energy.
- AC vs DC Misunderstanding: Direct Current (DC) flows in one direction—used in batteries, electronics. Alternating Current (AC) periodically reverses direction—used in household supply because it's efficient for long-distance transmission. They're not interchangeable.
Quick reference
- Newton's Laws: Inertia | F = ma | Action-Reaction pairs
- Electricity Units: Volt (potential) | Ampere (current) | Ohm (resistance) | Watt (power)
- Mirror Uses: Concave (shaving, dentist, telescope) | Convex (vehicle rear-view, security)
- Lens Uses: Convex (magnifying glass, camera, eyeglasses for farsightedness) | Concave (eyeglasses for nearsightedness)
- Light Phenomena: Reflection (bouncing back) | Refraction (bending) | Dispersion (splitting into colors)
Check yourself: 3 questions
1. Which of the following is the SI unit of electric current?
2. Which phenomenon is responsible for the blue colour of the sky?
3. The SI unit of electric current is:
This lesson is cut from the topic's note, not rewritten. Fact-checked on 17 Oct 2026: an AI-assisted check of this note against cited sources; the errors it found were corrected that day. Some errors may remain. The questions are from Shishya's validated question bank.
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