Physics Passing Package | Class 10 Science

MG SCHOOL SCIENCE PRESENTS

CLASS 10 PHYSICS
PASSING PACKAGE

Most Important Concepts • Definitions • SI Units • Formulas

SSLC EXAMINATION REVISION NOTES

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

1. ELECTRICITY

SI Units

Physical Quantity	Symbol	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

Electric Components and Measuring Instruments

Voltmeter: It measures the voltage. Connected in parallel.

Ammeter: It measures the current. Connected in series.

Definitions and Key Terms

Electric Current: Flow of electric charge through a conductor.
Formula: I = Q/t

Define 1 Ampere: 1 A = 1 C / 1 s

Potential Difference: Work done to move electric charge.
Formula: V = W/Q

Define 1 Volt: 1 V = 1 J / 1 C

Resistance: Opposition offered to the flow of current.

Define 1 Ohm: 1 Ω = 1 V / 1 A

Factors Affecting Resistance

• Length (R ∝ l)
• Thickness / Area of cross-section (R ∝ 1/A)
• Materials
• Temperature

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

Series and Parallel Combination of Resistors

Series Combination	Parallel Combination
Resistance increases.	Resistance decreases.
Current is the same.	Current is divided.
Voltage is divided.	Voltage is the same.
If one device fails, the other does not work.	If one device fails, the other works properly.

Series ResistanceRs = R1 + R2 + R3

Parallel Resistance1/Rp = 1/R1 + 1/R2 + 1/R3

Joule's Law of Heating

Heat produced in a conductor is directly proportional to:

• Square of current (I²)
• Resistance (R)
• Time (t)

H = I²Rt

Electric Power

Electric power is the rate at which electric energy is consumed in an electric circuit.
P = VI

Important Physics Formulas

Electric CurrentI = Q/t

Potential DifferenceV = W/Q

Ohm's LawV = IR

Series ResistanceRs = R1 + R2 + R3

Parallel Resistance1/Rp = 1/R1 + 1/R2 + 1/R3

Joule's HeatingH = I²Rt

Electric PowerP = VI

Electrical EnergyE = P × t

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. It is connected in series. If current is high, it becomes hot, melts and breaks the circuit.
• Heating Devices: Electric toaster, electric oven, electric kettle, electric bulb and electric fuse.
• Alloys: Nichrome is used in electrical heating devices because of its high melting point and high resistance.

⭐ Quick Revision – Electricity

• SI unit of current – Ampere.
• SI unit of charge – Coulomb.
• SI unit of resistance – Ohm.
• Voltmeter – Parallel connection.
• Ammeter – Series connection.
• Ohm's law – V = IR.
• Joule's law – H = I²Rt.
• Commercial unit – kWh.

2. MAGNETIC EFFECTS OF ELECTRIC CURRENT

Magnetic Field and Its Properties

Magnetic Field: The region around a magnet where magnetic force can be experienced.

Properties of Magnetic Field Lines:

• Magnetic field lines 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.

Activity: Tracing Field Lines Using 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.
4. Move the needle to a new position.
5. Continue step by step till you reach the South pole.
6. Join the points marked on the paper. This curve represents a magnetic field line.

Why do two magnetic field lines never intersect?
If two field lines cross each other, the compass needle would show two directions at the point of intersection, which is not possible.

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 magnetic field.

Direction of Current	Magnetic Field Direction
Upward	Anticlockwise
Downward	Clockwise

Solenoid and Electromagnet

Solenoid: A circular coil of insulated copper wire.

• Magnetic field in a solenoid is the same as that of a bar magnet.
• Inside the solenoid, the magnetic field is uniform.
• When a soft iron core is placed inside a solenoid, it is converted into an electromagnet.

Strength of magnetic field in a solenoid increases by:

1. Increasing current.
2. Increasing the number of turns of the coil.

Magnetic Field in a Circular Loop: Magnetic field lines are circular around the loop and nearly straight at the centre.

Fleming's Left-Hand Rule

Finger	Represents
Thumb	Motion / Force
Forefinger	Magnetic Field
Middle Finger	Current

Activity: Force on 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.

Domestic Electric Circuits and Hazards

Short Circuit: When live wire and neutral wire come in direct contact, it causes a short circuit.

Overloading: Connecting too many devices to a single socket or a sudden hike in voltage may cause overloading.

Prevention of Short Circuit and Overloading

• Use good-quality wires.
• 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.

⭐ Quick Revision – Magnetic Effects

• Magnetic field lines never intersect.
• Outside magnet: North to South.
• Inside magnet: South to North.
• Right-hand thumb rule gives magnetic field direction.
• Soft iron core is used in an electromagnet.
• Fleming's left-hand rule gives force direction.
• Earth wire protects from electric shock.

3. LIGHT – REFLECTION AND REFRACTION

Reflection of Light and Laws

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

Laws of Reflection:

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

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.

Concave and Convex Mirrors

Concave Mirror	Convex Mirror
Reflecting surface curved inwards.	Reflecting surface curved outwards.
Converging mirror.	Diverging mirror.
Can form real and inverted images.	Forms virtual and erect images.
Focal length negative (−ve).	Focal length positive (+ve).
Torches, search lights, vehicle headlights, shaving mirrors, dentist mirrors and solar furnaces.	Rear-view mirrors in vehicles because they give erect and diminished images.

Mirror Formulas

Mirror Formula1/v + 1/u = 1/f

Magnificationm = h'/h = −v/u

Radius of CurvatureR = 2f

Refraction of Light and 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:

1. Incident ray, refracted ray and normal all lie on the same plane.
2. sin i / sin r = Constant (Snell's Law).

Convex and Concave Lenses

Convex Lens	Concave Lens
Thicker in the middle and thinner at the edges.	Thicker at the edges and thinner in the middle.
Converging lens.	Diverging lens.
Can form real and inverted images.	Forms virtual and erect images.
Focal length positive (+ve).	Focal length negative (−ve).

Refractive Index, Lens Formula and Magnification

Refractive Index: Ratio of speed of light in air to 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.
• Refractive index of diamond is 2.42.

Lens Formula1/v − 1/u = 1/f

Magnificationm = h'/h

Refractive Indexn = c/v

Magnification:

• Positive – Virtual and erect image.
• Negative – Real and inverted image.
• m greater than 1 – Magnified image.
• m less than 1 – Diminished image.
• m = 1 – Same-size image.

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 whose focal length is 1 metre.
• Power of convex lens is positive (+ve).
• Power of concave lens is negative (−ve).

⭐ Quick Revision – Light

• Law of reflection: i = r.
• Concave mirror: Converging mirror.
• Convex mirror: Diverging mirror.
• Mirror formula: 1/v + 1/u = 1/f.
• Lens formula: 1/v − 1/u = 1/f.
• Refractive index: n = c/v.
• Power of lens: P = 1/f.
• SI unit of power: Dioptre.

4. HUMAN EYE AND COLOURFUL WORLD

Human Eye Parts and Accommodation

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 image is formed.

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

Accommodation of Eye

Near Objects	Distant Objects
Ciliary muscles contract.	Ciliary muscles relax.
Lens becomes thick.	Lens becomes thin.
Focal length decreases.	Focal length increases.

Near Point: 25 cm.
Far Point: Infinity.

Defects of Vision and Corrections

Defect	Problem	Causes	Correction
Myopia Nearsightedness	Cannot see distant objects clearly.	Excessive curvature of eye lens; elongation of eyeball.	Concave lens.
Hypermetropia Farsightedness	Cannot see near objects clearly.	Focal length of eye lens is too long; eyeball is too small.	Convex lens.
Presbyopia	Difficulty seeing near or far objects clearly.	Weakening of ciliary muscles; decreasing flexibility of eye lens.	Bifocal lens.
Cataract	Eye lens becomes milky and cloudy in old age.	Clouding of the eye lens.	Surgery.

Atmospheric Phenomena and Light Effects

Dispersion: Splitting of white light into seven colours. The band of seven colours is called the spectrum.

Important:

• Red bends the least.
• Violet bends the 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 continuously changing refractive index of air layers.

Why Planets Do Not Twinkle: Planets do not twinkle because they are closer to Earth and act as extended sources of light which nullify the twinkling effect.

Tyndall Effect: Path of light becomes visible due to scattering of light by colloidal particles.

Why Does the Sky Appear Blue? Atmospheric fine particles scatter blue light more strongly because blue light has a shorter wavelength than red light.

⭐ Quick Revision – Human Eye and Colourful World

• Near point – 25 cm.
• Far point – Infinity.
• Myopia – Concave lens.
• Hypermetropia – Convex lens.
• Presbyopia – Bifocal lens.
• Cataract – Surgery.
• Dispersion – Splitting of white light.
• Red bends least.
• Violet bends most.
• Twinkling of stars – Atmospheric refraction.
• Blue sky – Scattering of light.

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CLASS 10 PHYSICS PASSING PACKAGE

Revision material prepared from the supplied Physics Passing Package PDF.