MG SCHOOL SCIENCE • CLASS 10
PHYSICS PASSING PACKAGE
Complete Chapter-wise Important Notes, Definitions & Formulas
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⚡ CHAPTER 1 – ELECTRICITY
1.1 SI Units of Physical Quantities
| Physical Quantity | Symbol | SI Unit |
|---|---|---|
| Electric Current | I | Ampere (A) |
| Electric Charge | Q | Coulomb (C) |
| Electric Power | P | Watt (W) |
| Potential Difference | V | Volt (V) |
| Resistance | R | Ohm (Ω) |
| Resistivity | ρ | Ohm metre (Ω m) |
| Commercial Unit of Electricity | E | kWh |
1.2 Electric Components and Measuring Instruments
VoltmeterMeasures potential difference (voltage). Connected in parallel.
AmmeterMeasures electric current. Connected in series.
1.3 Definitions and Key Terms
Electric Current:
Flow of electric charge through a conductor.
I = Q / t
Define 1 Ampere:
1 A = 1 C / 1 s
Potential Difference:
Work done in moving an electric charge.
V = W / Q
Define 1 Volt:
1 V = 1 J / 1 C
Resistance: Opposition offered to the flow of electric current.
Define 1 Ohm:
1 Ω = 1 V / 1 A
1.4 Factors Affecting Resistance
Resistance of a conductor depends on:
- Length of conductor: R ∝ l
- Area of cross-section: R ∝ 1/A
- Nature of material
- Temperature
R = ρl / A
1.5 Ohm's Law
At constant temperature, the potential difference across a conductor is directly proportional to the current flowing through it.
V ∝ I
V = IR
1.6 Series and Parallel Combination of Resistors
Series Combination
- Resistance increases.
- Current is the same.
- Voltage is divided.
Rs = R1 + R2 + R3
Parallel Combination
- Resistance decreases.
- Current is divided.
- Voltage is the same.
1/Rp = 1/R1 + 1/R2 + 1/R3
| Series | Parallel |
|---|---|
| Same current | Same voltage |
| Voltage divided | Current divided |
| Resistance increases | Resistance decreases |
| Failure affects all devices | Other devices work if one fails |
1.7 Joule's Law of Heating
Heat produced in a conductor is directly proportional to:
- Square of current
- Resistance
- Time
H = I²Rt
Applications:
- Electric toaster
- Electric oven
- Electric kettle
- Electric bulb
- Electric fuse
Alloys such as nichrome are used in heating devices because of their high melting point and high resistance.
1.8 Electric Power and Energy
Electric Power: Rate at which electrical energy is consumed in an electric circuit.
P = VI
Electrical Energy:
E = P × t
1.9 Electric Devices and Important Facts
- Bulb filament: Tungsten, because of its high melting point and high resistance.
- Bulb gas: Argon / Nitrogen, because they increase the life of the filament.
- Working of electric bulb: Current passes through the filament, making it hot and causing it to emit light.
- Fuse: A safety device connected in series. When excessive current flows, it becomes hot, melts and breaks the circuit.
1.10 Important Formulas – Electricity
Electric Current: I = Q / t
Potential Difference: V = W / Q
Ohm's Law: V = IR
Series: Rs = R1 + R2 + R3
Parallel: 1/Rp = 1/R1 + 1/R2 + 1/R3
Heating Effect: H = I²Rt
Electric Power: P = VI
Electric Energy: E = P × t
🧲 CHAPTER 2 – MAGNETIC EFFECTS OF ELECTRIC CURRENT
2.1 Magnetic Field and Its Properties
Magnetic Field: Region around a magnet where magnetic force can be experienced.
Properties of Magnetic Field Lines:
- They never intersect each other.
- They form closed loops.
- Outside the magnet, direction is North pole to South pole.
- Inside the magnet, direction is South pole to North pole.
Why do two magnetic field lines never intersect?
If two lines cross each other, the compass needle would show two directions at the point of intersection, which is not possible.
If two lines cross each other, the compass needle would show two directions at the point of intersection, which is not possible.
2.2 Activity – Tracing Magnetic Field Lines Using a Compass
- Place a bar magnet on a white sheet of paper and mark its boundary.
- Place a compass needle near the North pole of the magnet.
- Mark the positions of the two ends of the needle.
- Move the compass needle to a new position.
- Continue step by step until you reach the South pole.
- Join the marked points. The curve represents a magnetic field line.
2.3 Right Hand Thumb Rule
- Hold the current-carrying conductor in your right hand.
- Thumb points in the direction of current.
- Four curled fingers show the direction of the magnetic field.
Current upwardMagnetic field direction: Anticlockwise.
Current downwardMagnetic field direction: Clockwise.
2.4 Solenoid and Electromagnet
Solenoid: A circular coil of insulated copper wire.
- Magnetic field in a solenoid is similar to that of a bar magnet.
- Magnetic field inside the solenoid is uniform.
- Increasing the current.
- Increasing the number of turns of the coil.
2.5 Fleming's Left Hand Rule
Stretch the thumb, forefinger and middle finger of the left hand mutually perpendicular to each other.
ThumbMotion / Force
ForefingerMagnetic Field
Middle FingerCurrent
2.6 Activity – Force on a Current-Carrying Conductor
- An aluminium rod is placed between the poles of a horseshoe magnet.
- When current is passed, the rod moves in one direction.
- When current is reversed, the rod moves in the opposite direction.
2.7 Domestic Electric Circuits and Hazards
Short Circuit: If the live wire and neutral wire come in direct contact, it causes a short circuit.
Overloading: Overloading can occur due to connecting too many devices to a single socket or a sudden rise in voltage.
Precautions against short circuit and overloading:
- Use good-quality wires.
- Use a fuse.
- Do not connect many devices to a single socket.
- Do not use faulty electrical devices.
2.8 Functions of Earth Wire
- Provides a low-resistance path.
- Sends leakage current to the ground.
- Prevents electric shock to the user.
💡 CHAPTER 3 – LIGHT: REFLECTION AND REFRACTION
3.1 Reflection of Light and Laws
Reflection of Light: Bouncing back of light when it falls on a reflecting surface.
Laws of Reflection:
- Angle of incidence is equal to angle of reflection.
- Incident ray, reflected ray and normal all lie in the same plane.
∠i = ∠r
3.2 Important Terms in Spherical Mirrors
- Pole (P): Centre of the spherical mirror.
- Centre of Curvature (C): Centre of the sphere of which the mirror forms a part.
- Principal Focus of Concave Mirror (F): Parallel incident rays actually meet at a point after reflection.
- Principal Focus of Convex Mirror (F): Parallel incident rays appear to meet at a point after reflection.
- Principal Axis: Line passing through C and P.
- Radius of Curvature (R): Distance between C and P.
- Focal Length (f): Distance between F and P.
R = 2f
3.3 Concave and Convex Mirrors
| Concave Mirror | Convex Mirror |
|---|---|
| Reflecting surface curves inwards. | Reflecting surface curves outwards. |
| Converging mirror. | Diverging mirror. |
| Can form real and inverted images. | Forms virtual and erect images. |
| Focal length is negative. | Focal length is positive. |
| Torches, searchlights, headlights, shaving mirrors, dentist mirrors and solar furnaces. | Rear-view mirrors in vehicles. |
Convex mirrors are used as rear-view mirrors because they give erect and diminished images.
3.4 Mirror Formula and Magnification
Mirror Formula: 1/v + 1/u = 1/f
Magnification: m = h'/h = -v/u
3.5 Refraction of Light and Laws
Refraction of Light: Bending of light when it travels from one medium to another.
- Rarer to denser medium: Light bends towards the normal.
- Denser to rarer medium: Light bends away from the normal.
- Light travels faster in a rarer medium than in a denser medium.
- Incident ray, refracted ray and normal all lie in the same plane.
- The ratio of sine of angle of incidence to sine of angle of refraction is constant.
sin i / sin r = Constant
This is known as Snell's Law.
3.6 Convex and Concave Lenses
| Convex Lens | Concave Lens |
|---|---|
| Thicker in the middle. | Thinner in the middle. |
| Thinner at edges. | Thicker at edges. |
| Converging lens. | Diverging lens. |
| Can form real and inverted images. | Forms virtual and erect images. |
| Positive focal length. | Negative focal length. |
3.7 Refractive Index
Refractive index is the ratio of the speed of light in air to the speed of light in a medium.
n = c / v
- Higher refractive index: Medium is optically denser and speed of light decreases.
- Lower refractive index: Medium is optically rarer and speed of light increases.
The refractive index of diamond is 2.42. This means the ratio of the speed of light in air to that in diamond is 2.42.
3.8 Lens Formula and Magnification
Lens Formula: 1/v - 1/u = 1/f
Magnification: m = h' / h
- Positive magnification: Virtual and erect image.
- Negative magnification: Real and inverted image.
- m > 1: Magnified image.
- m < 1: Diminished image.
- m = 1: Same-size image.
- m = +2: Magnified virtual and erect image (for example, by a convex lens).
3.9 Power of Lens
Power of a lens is the reciprocal of its focal length in metres.
P = 1 / f
- SI unit: Dioptre (D).
- 1 dioptre is the power of a lens with focal length 1 metre.
- Convex lens: Positive power.
- Concave lens: Negative power.
👁 CHAPTER 4 – HUMAN EYE AND COLOURFUL WORLD
4.1 Human Eye Parts and Functions
| Part | Function |
|---|---|
| Pupil | Controls the amount of light entering the eye. |
| Iris | Controls the size of the pupil. |
| Ciliary Muscles | Change the focal length of the eye lens. |
| Retina | Screen on which the image is formed. |
4.2 Accommodation of the Eye
To see a near object
Ciliary muscles contract → Lens becomes thick → Focal length decreases.
To see a distant object
Ciliary muscles relax → Lens becomes thin → Focal length increases.
Near Point = 25 cm
Far Point = Infinity
4.3 Defects of Vision and Their Corrections
1. Myopia (Nearsightedness)
2. Hypermetropia (Farsightedness)
3. Presbyopia
4. Cataract
- Person can see near objects clearly but cannot see distant objects clearly.
- Causes: Excessive curvature of eye lens or elongation of eyeball.
- Correction: Concave lens.
Myopia → Concave Lens
2. Hypermetropia (Farsightedness)
- Person can see distant objects clearly but cannot see near objects clearly.
- Causes: Focal length of eye lens is too long or eyeball has become too small.
- Correction: Convex lens.
Hypermetropia → Convex Lens
3. Presbyopia
- Occurs in old age.
- Person cannot see near or far objects clearly.
- Causes: Weakening of ciliary muscles and decreasing flexibility of eye lens.
- Correction: Bifocal lens.
Presbyopia → Bifocal Lens
4. Cataract
- Eye lens becomes milky and cloudy in old age.
- Correction: Surgery.
4.4 Dispersion and Spectrum
Dispersion: Splitting of white light into seven colours.
Spectrum: The band of seven colours obtained by dispersion of white light.
VIBGYOR
- Red bends the least.
- Violet bends the most.
4.5 Formation of Rainbow
Rainbow formation is caused by dispersion of sunlight by tiny water droplets in the atmosphere acting like small prisms, combined with internal reflection.
4.6 Twinkling of Stars
Stars twinkle due to atmospheric refraction of starlight caused by continuously changing refractive index of different layers of air.
4.7 Why Do Planets Not Twinkle?
Planets do not twinkle because they are closer to Earth and act as extended sources of light. The variations in light from different parts of the planet tend to cancel each other.
4.8 Tyndall Effect
The phenomenon in which the path of light becomes visible due to scattering of light by colloidal particles is called the Tyndall effect.
4.9 Why Does the Sky Appear Blue?
Fine particles in the atmosphere scatter blue light more strongly because blue light has a shorter wavelength than red light.
⭐ QUICK REVISION – IMPORTANT FORMULAS
Electric CurrentI = Q / t
Potential DifferenceV = W / Q
Ohm's LawV = IR
Electric PowerP = VI
Heating EffectH = I²Rt
Electric EnergyE = P × t
Mirror Formula1/v + 1/u = 1/f
Mirror Magnificationm = -v/u
Lens Formula1/v - 1/u = 1/f
Refractive Indexn = c/v
Power of LensP = 1/f
Radius of CurvatureR = 2f
📚 EXAM PREPARATION TIP
Revise all definitions, SI units, laws, formulas, applications and lens corrections. Practise numerical problems and important diagrams separately.
Revise all definitions, SI units, laws, formulas, applications and lens corrections. Practise numerical problems and important diagrams separately.
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