Physics — Physical Component
Overview
Physics forms a core part of the Science section in TS TET Paper II, targeting teachers for classes VI–VIII. This component tests your understanding of fundamental physical concepts that upper primary students encounter: force, motion, energy, heat, light, sound, electricity, and magnetism. Questions typically assess conceptual clarity rather than heavy calculations, so focus on understanding principles, definitions, and real-life applications.
The examiner often frames questions around everyday phenomena—why a ball stops rolling, how a mirror forms an image, why metals feel cold. Mastering this section requires you to think like a teacher explaining concepts to a 12-year-old: simple, clear, and connected to daily life.
Key Concepts
- Force changes motion or shape: A force can start, stop, speed up, slow down, or change the direction of a moving object. It can also change an object's shape (stretching a rubber band).
- Friction opposes relative motion: Friction acts between surfaces in contact and always opposes the direction of motion. It depends on the nature of surfaces and the normal force, not on the area of contact.
- Energy is conserved but transforms: Energy cannot be created or destroyed—only converted from one form to another. A swinging pendulum converts potential energy to kinetic energy and back.
- Heat flows from hot to cold: Heat transfer occurs through conduction (solids), convection (fluids), and radiation (no medium needed). Temperature measures the degree of hotness; heat is the total energy transferred.
- Light travels in straight lines: This explains shadows, eclipses, and pinhole cameras. Reflection follows the law: angle of incidence = angle of reflection. Refraction bends light when it changes medium.
- Sound needs a medium: Sound is a longitudinal wave requiring a material medium (solid, liquid, or gas). It cannot travel through vacuum. Speed of sound is highest in solids, lowest in gases.
- Current flows in a closed circuit: Electric current is the flow of charges. A complete circuit with a source (cell/battery), conductor, and load is needed. Conductors allow current; insulators block it.
- Magnets have two poles: Like poles repel; unlike poles attract. A freely suspended magnet aligns north-south. Electromagnets are temporary magnets made by passing current through a coil.
Formulas / Key Facts
Force and Motion
- Force = Mass × Acceleration (F = ma) — relates force to mass and rate of velocity change
- Pressure = Force ÷ Area (P = F/A) — smaller area means greater pressure for same force
- Work = Force × Distance (W = F × d) — work done when force moves an object
Simple Machines
- Mechanical Advantage (MA) = Load ÷ Effort — measures how much a machine multiplies force
- Types of levers: Class I (fulcrum between load and effort), Class II (load between), Class III (effort between)
Heat
- Heat gained/lost = Mass × Specific heat × Temperature change (Q = mcΔT)
- Good conductors: metals (silver best, then copper, aluminium)
- Poor conductors (insulators): wood, plastic, air, wool
Light
- Law of reflection: Angle of incidence (i) = Angle of reflection (r)
- Real image: formed by actual intersection of rays; can be caught on screen
- Virtual image: formed by apparent intersection; cannot be caught on screen (mirror images)
Sound
- Speed of sound in air at 20°C ≈ 343 m/s
- Frequency (Hz) × Wavelength = Speed of sound
- Audible range for humans: 20 Hz to 20,000 Hz
Electricity
- Ohm's Law: V = IR (Voltage = Current × Resistance)
- Series circuit: same current through all components; total resistance = R₁ + R₂ + ...
- Parallel circuit: same voltage across all branches; total resistance decreases
Worked Examples
Example 1: Force and Pressure A book of weight 10 N rests on a table. The book's base area is 200 cm². Find the pressure exerted on the table.
Solution:
- Force (weight) = 10 N
- Area = 200 cm² = 200 × 10⁻⁴ m² = 0.02 m²
- Pressure = Force ÷ Area = 10 ÷ 0.02 = 500 N/m² (or 500 Pa)
Example 2: Reflection of Light A ray of light strikes a plane mirror at 35° to the mirror surface. Find the angle of reflection.
Solution:
- Angle to surface = 35°, so angle of incidence = 90° − 35° = 55°
- By law of reflection, angle of reflection = angle of incidence = 55°
Example 3: Ohm's Law A bulb has resistance 20 Ω and is connected to a 6 V battery. Calculate the current flowing through it.
Solution:
- V = IR → I = V/R = 6/20 = 0.3 A (or 300 mA)
Common Mistakes
❌ Confusing mass and weight → Mass is the amount of matter (measured in kg); weight is the gravitational force on that mass (measured in N). Weight = mass × g.
❌ Thinking friction always opposes motion → Friction opposes relative motion. When you walk, friction actually helps by pushing you forward (static friction prevents slipping).
❌ Believing light bends toward the normal in all cases → Light bends toward the normal when entering a denser medium and away from the normal when entering a rarer medium.
❌ Assuming sound travels fastest in air → Sound travels fastest in solids (particles are closest), then liquids, then gases. Steel conducts sound about 15 times faster than air.
❌ Mixing up series and parallel characteristics → In series: current is same everywhere, voltage divides. In parallel: voltage is same across branches, current divides.
❌ Thinking magnets attract all metals → Only ferromagnetic materials (iron, cobalt, nickel, and their alloys) are attracted to magnets. Aluminium, copper, and gold are not attracted.
Quick Reference
- Force changes motion or shape; friction always opposes relative motion between surfaces.
- Work is done only when force causes displacement in its direction.
- Heat transfers by conduction, convection, or radiation; metals are good conductors.
- Angle of incidence equals angle of reflection; light bends when changing medium.
- Sound needs a medium; it travels fastest in solids, slowest in gases.
- Ohm's Law: V = IR; current needs a closed circuit to flow.