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● Lungs are situated in the thoracic chamber which is anatomically an air-tight chamber.

● The thoracic chamber is formed dorsally by the vertebral column,ventrally by the sternum, laterally by the ribs and on the lower side by the dome-shaped diaphragm.

● The anatomical setup of lungs in thorax is such that any change in the volume of the thoracic cavity will be reflected in the lung (pulmonary) cavity.

● Such an arrangement is essential for breathing,as we cant directly alter the pulmonary volume

● Lungs are covered by a double layered pleura with pleural fluid between them.It reduces friction on the lung-surface. 

● Outer pleural membrane is in close contact with the thoracic lining Inner pleural membrane is in contact with the lung surface.

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PRINCIPLE OF HOMOGENEITY

➨ The magnitude of a physical quantity may be added or subtracted from each other only if they have the same dimension, also the dimension on both sides of an equation must be same.This is called as principle of homogeneity.

Dimensional Variables

➨ Dimensional variables are those physical quantities which have dimensions and do not have fixed value.

❖ E.g., velocity, acceleration, force, work, power... etc.

Dimensionless Variables

➨Dimensionless variables are those physical quantities which do not have dimensions and do not have fixed value.,

❖ E.g., Specific gravity, refractive index, Coefficient of friction, Poisson’s Ratio etc.,

ℙ𝕝𝕒𝕟𝕔𝕜'𝕤 ℚ𝕦𝕒𝕟𝕥𝕦𝕞 𝕋𝕙𝕖𝕠𝕣𝕪
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❖ Substances that absorb or emit light discontinuously in the form of small packets or bundles.

❖ The smallest packet of energy is called quantum (plural quanta).

❖ The radiation is propagated in the form of waves.

❖ The energy of a quantum is directly proportional to the frequency of the radiation

E ∝ v
E = hv
E = (hc)/ λ =hc v

Where E = Energy of radiation
h = Planck's constant
= 6.626 * 10^-27 * erg .sec
= 6.626 * 10^-34 Joule.sec

❖ A body that can absorb or emit energy in whole number multiple of quantum.

E = nhv

Where n = 1, 2, 3, 4

❖ The frequency of emitted radiation goes from lower to higher as the temperature increases.

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♻️ Important Notes - Electrochemical Cells ♻️

► An electrochemical cell can convert electrical energy to chemical energy and can also convert electrical energy to chemical energy. There are two types of electrochemical cells- Galvanic cell and Electrolytic cell.

► Cathodes are usually metal electrodes. It is the electrode where reduction takes place. The cathode is the positive electrode in a galvanic cell and a negative electrode in an electrolytic cell. Electrons move into the cathode.

► A half-cell is half of an electrochemical cell (electrolytic or galvanic), where either oxidation or reduction occurs. At equilibrium, there is no transfer of electrons across the half cells. Therefore, the potential difference between them is nil.

► A salt bridge is a device used to connect the oxidation and reduction half-cells of a galvanic cell (a type of electrochemical cell). Strong electrolytes are generally used to make the salt bridges in electrochemical cells. Since ZnSO4 is not a strong electrolyte, it is not used to make salt bridges.

► Emf of a cell is equal to the maximum potential difference across its electrodes, which occurs when no current is drawn through the cell. It can also be defined as the net voltage between the oxidation and reduction half-reactions.

► Cell potential is an intensive property as it is independent of the amount of material present. Gibbs free energy is defined for an electrochemical cell and is an extensive property as it depends on the quantity of the material.

► Electrode potential is the tendency of an electrode to accept or to lose electrons. Electrode potential depends on the nature of the electrode, temperature of the solution and the concentration of metal ions in the solution. It doesn’t depend on the size of the electrode.

► The salt bridge connects the two half-cell solutions to complete the circuit of the electrochemical cell. The electrolytes of the salt bridge are generally prepared in agar-agar or gelatin so that the electrolytes are kept in a semi-solid phase and do not mix with the half-cell solutions and interfere with the electrochemical reaction.

► A salt bridge is a junction that connects the anodic and cathodic compartments in a cell or electrolytic solution. It maintains electrical neutrality within the internal circuit, preventing the cell from rapidly running its reaction to equilibrium.

► A Voltaic or Galvanic cell is a type of electrochemical cell that converts chemical energy into electrical energy. Photovoltaic cells are used to convert light energy into electrical energy. An Electrolytic cell is a type of electrochemical cell that converts electrical energy into chemical energy. A fuel cell is an electrochemical cell that converts the chemical energy of a fuel and an oxidizing agent into electricity.

► For all spontaneous chemical reactions, the change in Gibbs free energy (ΔG°) is always negative. For a spontaneous reaction in an electrolytic cell, the cell potential (E°cell) should be positive.

► In an electrochemical cell, when an opposing externally potential is applied and increased slowly, the reaction continues to take place. When the external potential is equal to the potential of the cell, the reaction stops. Once the externally applied potential is greater than the potential of the cell, the reaction goes in the opposite direction and the cell behaves like an electrolytic cell.

► Primary cells cannot be used again and again. Since there is no fluid inside, these cells are also known as dry cells. The internal resistance is high and the chemical reaction is irreversible. Their initial cost is cheap.

► A secondary battery (a series of cells) is one which can be charged, discharged into a load, and recharged many times. Nickel-cadmium cell, Lead storage cell and Mercury cell are examples of secondary cells. Leclanche cell is an example of a primary cell.

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➡️Electrochemistry short notes