DIFFERENCES FROM PAST PAPERS (1994)

1. Artery & Vein

Artery
i) Arteries are blood vessels which transport blood away from the heart.
ii) Arteries have thick vascular walls.
iii) The inside bore or lumen of arteries is narrow.
iv) Arteries carry oxygenated blood with the exception of pulmonary artery.
v) The walls of arteries are more elastic.
vi) The blood is under great pressure in the arteries.
vii) Arteries are generally deeply placed.
viii) Arteries end in the capillaries.

Vein:
i) Veins are the blood vessels which always carry blood towards heart.
ii) Veins have thin muscular walls.
iii) The inside bore or lumen of veins is wide.
iv) Veins carry deoxygenated blood with the exception of pulmonary veins.
v) The walls of veins are less elastic.
vi) The blood is under less pressure in the veins.
vii) Veins are generally superficially placed.
viii) Veins start from the capillaries.

2. PNP and NPN Transistor

1. NPN has higher electron mobility than PNP. Therefore, NPN bipolar transistors are often more favoured than PNP transistors.
2. NPN is easier to create from silicon than PNP.
3. The main difference of NPN and PNP is the base. One is just the opposite of the other.
4. With the NPN, a P-dope semiconductor is the base, while with the PNP, the ‘base’ is a N-dope semiconductor.

3. Electronic & Static Electricity

Electronic Electricity
i) This is electricity in motion.
ii) It involves flow of electrons.
iii) It has high voltage.

Static Electricity:
i) This is electricity at rest.
ii) It does not involve flow of electrons.
iii) It has low voltage.

4. Concave & Convex Lens

Concave Lens
i) It is the lens which is narrower in the centre and broader towards the corners.
ii) When a beam of light strikes a concave lens all the rays after passing through it diverge.
iii) It gives mostly virtual image.
iv) They are also called diverging lenses.

Convex Lens:
i) It is the lens which is narrower towards the corners and broader towards the centre.
ii) When a beam of light strikes a convex lens all the rays after passing through it converge at a single point.
iii) Mostly real images are formed except when the ray of light passes through it when object is palced between optical centre and focus.
iv) They are also called converging lenses.

5. Absorption & Adsorption

Absorption
i) Absorption is a process in which a substance takes up another substance, such as blotting paper (solid) absorbing water (a liquid). OR Adsorption and absorption are two different things. Absorption is the chemical integration of one chemical into another. When you drink a glass of water, you are absorbing it, as the water becomes part of you.

Adsorption:
i) Adsorption is a process in which a substance adheres to the surface of another substance. Adsorption is important in some types of catalysis, notably where gases adsorb on metal surfaces. The reaction is then made easier by a consequent lowering of activation energy. OR Adsorption occurs when one substance holds another via physical bonds. If you spill a glass of water on your shirt, it is adsorbed as the fibres will hold the water until heat dries out the shirt.

6. Fats & Oils

Fats
i) are solid at room temperature
ii) made by animals, mostly
iii) are more saturated

Oils:
i) are liquid at room temperature
ii) are made by plants, mostly
iii) are less saturated