1. Ohm’s Law
The potential difference between two points is directly proportional to the electric current at a constant temperature.
Formula: V ∝ I → V = IR
2. Joule’s Law of Heating Effect
The heat produced in a conductor is directly proportional to:
- The square of the current (I2) passing through it.
- The resistance (R).
- The time (t) for which the current is passed.
Formula: H = I2Rt
3. Right-Hand Thumb Rule
When you wrap your right hand around a solenoid with your fingers in the direction of the conventional current, your thumb points in the direction of the magnetic pole.
4. Fleming’s Right-Hand Rule
Hold out the right hand with the forefinger, middle finger, and thumb perpendicular to each other:
- Forefinger: Direction of magnetic field.
- Thumb: Direction of motion.
- Middle finger: Direction of induced current.
5. Fleming’s Left-Hand Rule
Hold out the left hand with the forefinger, middle finger, and thumb perpendicular to each other:
- Forefinger: Direction of magnetic field.
- Thumb: Direction of motion of the coil.
- Middle finger: Direction of current.
6. Faraday’s Law
The rate at which the magnetic flux linked with a coil changes produces induced EMF or current. The greater the rate of change of magnetic flux, the greater the induced current, and vice versa.
7. Laws of Reflection of Light
I Law
The angle of incidence is equal to the angle of reflection.
II Law
The incident ray, the normal to the mirror at the point of incidence, and the reflected ray all lie in the same plane.
8. Laws of Refraction of Light
I Law
The incident ray, the refracted ray, and the normal to the interface of two transparent media at the point of incidence all lie in the same plane.
II Law – Snell’s Law
The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for light of a given colour and for a given pair of media.
Formula: sin i / sin r = constant
9. Law of Conservation of Mass
The law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction.
10. Dobereiner’s Law of Triads
The average of the atomic masses of the first and third elements in a triad will be roughly equal to the atomic mass of the second element in that triad.
11. Newlands’ Law of Octaves
When elements are arranged in increasing order of atomic masses, the properties of every eighth element are similar to those of the first element.
12. Mendeleev’s Periodic Law
The properties of the elements are periodic functions of their atomic masses.
13. Modern Periodic Law
The properties of the elements are periodic functions of their atomic numbers.
14. 10% Law
According to the 10% law, only about 10% of the energy entering a trophic level is available for transfer to the next trophic level.