Physics Passing Package | Class 10 Science

CLASS 10 PHYSICS

Passing Package • Important Definitions • Laws • Formulas • Quick Revision

MG SCHOOL SCIENCE

1. Electricity 2. Magnetic Effects 3. Light 4. Human Eye

⚡ Chapter 1 – Electricity

1. SI Units

Physical Quantity	Symbol / Formula	SI Unit
Electric Current	I	Ampere (A)
Electric Charge	Q	Coulomb (C)
Electric Power	P	Watt (W)
Potential Difference / Voltage	V	Volt (V)
Resistance	R	Ohm (Ω)
Resistivity	ρ	Ohm metre (Ω m)
Commercial Unit of Electricity	E	kWh

2. Electric Components & Measuring Instruments

VoltmeterMeasures voltage. Connected in parallel.

AmmeterMeasures current. Connected in series.

3. Definitions & Key Terms

• Electric current: Flow of electric charge through a conductor. Or I = Q / t.
• Define 1 A: 1 A = 1 C / 1 s.
• Potential difference: Work done to move an electric charge. Or V = W / Q.
• Define 1 V: 1 V = 1 J / 1 C.
• Resistance: Opposition to the flow of current.
• Define 1 ohm: 1 Ω = 1 V / 1 C. This expression is reproduced as printed in the supplied PDF; verify the unit before using it in an exam answer.

4. Factors Affecting Resistance

Resistance of a conductor depends on:

• Length: R ∝ l
• Thickness / Area of cross-section: R ∝ 1/A
• Material
• Temperature

5. Ohm's Law & Circuit Combinations

Ohm's Law: V ∝ I (at constant temperature) or V = IR

Series combination

• Resistance increases
• Current is the same
• Voltage is divided

Parallel combination

• Resistance decreases
• Current is divided
• Voltage is the same

6. Joule's Law of Heating & Applications

Heat produced in a conductor is directly proportional to current squared, resistance and time.

H = I²Rt

Advantages of parallel connection

• If one device fails, the other works properly.
• Same voltage supply to all appliances.
• Resistance decreases and current is divided.

Disadvantages of series connection

• If one device fails, the other does not work.
• Voltage is divided, resistance increases and the same current flows.

Electric power: Rate at which electric energy is consumed in an electric circuit.

7. Important Physics Formulas

I = Q / t

V = W / Q

V = IR

Rₛ = R₁ + R₂ + R₃

1/Rₚ = 1/R₁ + 1/R₂ + 1/R₃

H = I²Rt

P = VI

E = P × t

8. Electric Devices

• Electric bulb filament: Tungsten, because of its high melting point and high resistance.
• Electric bulb gas: Argon / Nitrogen, because they increase the life of the filament.
• Electric bulb working: When current passes through the filament, it becomes hot and emits light.
• Fuse: A safety device that protects the electric circuit. Connected in series. If current is high, it becomes hot, melts and breaks the circuit.
• Heating devices working on Joule's law: Electric toaster, electric oven, electric kettle, electric bulb and electric fuse.
• Alloys: Alloys like nichrome are used in electrical heating devices because of their high melting point and high resistance.

🧲 Chapter 2 – Magnetic Effects of Electric Current

1. Magnetic Field & Its Properties

Magnetic field: Force around the magnet.

Properties of magnetic field lines

• Never intersect each other.
• 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 not intersect?
If two lines cross each other, the compass needle would show two directions at the point of intersection, which is not possible.

2. Activity: Tracing Field Lines Using a Compass Needle

1. Place the bar magnet on a white paper and mark its boundary.
2. Place the compass needle near the North pole of the magnet.
3. Mark the position of the two ends of the needle. Then move the needle to a new position.
4. Proceed step by step until you reach the South pole of the magnet.
5. Join the points marked on the paper. This curve represents a field line.

3. Right-Hand Thumb Rule

• Hold the current-carrying conductor in your right hand.
• Thumb points in the direction of current.
• Four fingers wrapped around the conductor show the direction of the magnetic field.
• Current upward → magnetic field anticlockwise.
• Current downward → magnetic field clockwise.

4. Solenoid & Electromagnet

• Solenoid: Circular coil of insulated copper wire.
• Magnetic field in a solenoid is the same as a bar magnet; inside the solenoid it is uniform.
• Electromagnet: When a soft iron core is placed inside the solenoid, it is converted into an electromagnet.
• Strength of magnetic field in a solenoid increases by increasing current and increasing the number of turns of the coil.
• Magnetic field in a circular loop: Circles around the loop; straight lines at the centre.

5. Fleming's Left-Hand Rule & Activity

In the left hand:

ThumbMotion / Force

ForefingerMagnetic field

Middle fingerCurrent

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.

6. Domestic Electric Circuits & Hazards

• Short circuit: If the live wire and neutral wire come in direct contact, it causes a short circuit.
• Overloading: The PDF describes overloading as occurring when live and neutral wires come in direct contact, due to a sudden hike in voltage, or by connecting too many devices to a single socket.

Prevention / Precautions for short circuit & overloading

• Use good-quality wire.
• Use a fuse.
• Do not connect many devices to a single socket.
• Do not use faulty devices.

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

1. Reflection of Light & Laws

Reflection of light: Bouncing back of light when light falls on a reflecting surface.

• Angle of incidence = Angle of reflection (i = r).
• Incident ray, reflected ray and normal all lie on the same plane.

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): Incident rays parallel to the principal axis after reflection actually meet at a point.
• Principal focus of convex mirror (F): Incident rays parallel to the principal axis after reflection appear to meet at a point.
• Principal axis: Line passing through C and P.
• Radius of curvature (R): Distance between C and P. (R = 2f)
• Focal length (f): Distance between F and P.

3. Concave & Convex Mirrors

Concave mirror

• Reflecting surface curved inwards.
• Converging mirror.
• Real and inverted image (as listed in the PDF).
• Focal length negative (−ve).

Uses

Torches, search lights, vehicle headlights, shaving mirror, dentist mirror and solar furnaces.

Convex mirror

• Reflecting surface curved outwards.
• Diverging mirror.
• Virtual and erect image.
• Focal length positive (+ve).

Uses

Rear-view mirror in vehicles, because it gives an erect and diminished image.

4. Mirror Formulas

Mirror formula: 1/v + 1/u = 1/f

Magnification: m = h′ / h = −v / u

5. Refraction of Light & Laws

Refraction of light: Bending of light when light travels from one medium to another.

• Rarer to denser medium → bends towards the normal.
• Denser to rarer medium → bends away from the normal.
• Light travels faster in a rarer medium than in a denser medium.

Laws of refraction

• Incident ray, refracted ray and normal all lie on the same plane.
• sin i / sin r = constant (Snell's law).

6. Convex & Concave Lenses

Convex lens

• Thicker in the middle, thinner at the edge.
• Converging lens.
• Real and inverted image (as listed in the PDF).
• Focal length positive (+ve).

Concave lens

• Thicker at the edge, thinner in the middle.
• Diverging lens.
• Virtual and erect image.
• Focal length negative (−ve).

7. Refractive Index, Lens Formula & Magnification

Refractive index: n = c / v

• Refractive index is the ratio of the speed of light in air to the speed of light in a medium.
• Higher refractive index → medium is denser and speed of light decreases.
• Lower refractive index → medium is rarer and speed of light increases.
• Refractive index of diamond is 2.42. This means the ratio of speed of light in air to speed of light in diamond is 2.42.

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: Convex lens (as stated in the PDF).

8. Power of Lens

P = 1 / f (focal length in metres)

• SI unit is dioptre (D).
• 1 dioptre is the power of a lens whose focal length is 1 metre.
• Power of a convex lens is positive (+ve).
• Power of a concave lens is negative (−ve).

👁️ Chapter 4 – Human Eye and Colourful World

1. Human Eye Parts & Accommodation

• 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.
• Power of accommodation: Ability of the eye to see near and far objects by changing its focal length.

To see a near objectCiliary muscles contract → lens becomes thick → focal length decreases.

To see a distant objectCiliary muscles relax → lens becomes thin → focal length increases.

Near point = 25 cm   |   Far point = Infinity

2. Defects of Vision & Corrections

Myopia (Nearsightedness)

Person can see near objects clearly but cannot see far objects clearly.

Causes: Excessive curvature of eye lens; elongation of eyeball.

Correction: Concave lens.

Hypermetropia (Farsightedness)

Person can see far objects clearly but cannot see near objects clearly.

Causes: Focal length of eye lens is too long; eyeball has become too small.

Correction: Convex lens.

Presbyopia

Occurs in old age; person cannot see near or far objects clearly.

Causes: Weakening of ciliary muscles; decreasing flexibility of eye lens.

Correction: Bifocal lens.

Cataract

Eye lens becomes milky and cloudy in old age.

Correction: Surgery.

3. Atmospheric Phenomena & Light Effects

• Dispersion & spectrum: Splitting of white light into seven colours is called dispersion. The band of seven colours is called a spectrum. Red bends least; violet bends most.
• Rainbow formation: Caused by dispersion of sunlight by tiny water droplets in the atmosphere acting like small prisms, combined with internal reflection.
• Twinkling of stars: Due to atmospheric refraction of starlight caused by the continuously changing refractive index of air layers.
• Why planets do not twinkle: Planets are closer to Earth and act as extended sources of light, which nullify the twinkling effect.
• Tyndall effect: The path of light becomes visible due to scattering of light by colloidal particles.
• Why the sky appears blue: Fine atmospheric particles scatter blue light more strongly because blue light has a shorter wavelength than red light.

⭐ Quick Revision – Formula Bank

ElectricityI = Q/t
V = W/Q
V = IR
P = VI
E = P × t
H = I²Rt

ResistanceRₛ = R₁ + R₂ + R₃
1/Rₚ = 1/R₁ + 1/R₂ + 1/R₃

Mirrors1/v + 1/u = 1/f
m = h′/h = −v/u

Lenses & Lightn = c/v
1/v − 1/u = 1/f
P = 1/f

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