The resistance of a given object depends primarily on two factors: What material it is made of, and its shape. For a given material, the resistance is inversely proportional to the cross-sectional area; for example, a thick copper wire has lower resistance than an otherwise-identical thin copper wire. Also, for a given material, the resistance is proportional to the length; for example, a long copper wire has higher resistance than an otherwise-identical short copper wire. The resistance R and conductance G of a conductor of uniform cross section, therefore, can be computed as
<span />
where is the length of the conductor, measured in metres [m], A is the cross-sectional area of the conductor measured in square metres [m²], σ (sigma) is the electrical conductivity measured in siemens per meter (S·m−1), and ρ (rho) is the electrical resistivity (also called specific electrical resistance) of the material, measured in ohm-metres (Ω·m). The resistivity and conductivity are proportionality constants, and therefore depend only on the material the wire is made of, not the geometry of the wire. Resistivity and conductivity are reciprocals: . Resistivity is a measure of the material's ability to oppose electric current.
This formula is not exact, as it assumes the current density is totally uniform in the conductor, which is not always true in practical situations. However, this formula still provides a good approximation for long thin conductors such as wires.
Another situation for which this formula is not exact is with alternating current (AC), because the skin effect inhibits current flow near the center of the conductor. For this reason, the geometrical cross-section is different from the effective cross-section in which current actually flows, so resistance is higher than expected. Similarly, if two conductors near each other carry AC current, their resistances increase due to the proximity effect. At commercial power frequency, these effects are significant for large conductors carrying large currents, such as busbars in an electrical substation,[3] or large power cables carrying more than a few hundred amperes.
Answer:
permeability
Explanation:
dictionary definition: the state/quality of a material or membrane that causes it to allow liquids or gases to pass through it
in biology we use this term to describe the cell membrane, it is "semi-permeable" because it allows certain gasses and molecules to pass through
Answer:
B) splits carbon dioxide( mark me brainlest!)
Explanation:
In a nut shell , the light energy from the sun is converted into Chemical energy by the plants through the process of photosynthesis. The green pigment chlorophyll present in the leaves traps light energy from the sun . This light energy is used to convert water and carbon-dioxide into Glucose and Oxygen.
Proteins are the macromolecules made of hundreds of amino acids. Proteins are most varied class of biological molecules and show the greatest variety of structures. Many have detailed three-dimensional folding patterns that result in a compact form, but others do not fold up at all and they are in random conformations. The function of proteins depends on their structure.
The secondary structure of protein fold together to form the 3D arrangement of a polypeptide chain that results into Tertiary structure which is a functional protein.
The water can be used for cleaning, bathing (depending on how clean the water is), washing hands, toilet water etc
