Question

state law of resiatance and ohms law​

Answer 1

Answer:

Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. Therefore, V = RI where R is a constant called resistance. R depends on the dimensions of the conductor and also on the material of the conductor. Its SI unit is Ohm (Ω).

Explanation:

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Answer 2

Answer:

The following are the main laws of resistance:

(i) Resistance of a conductor is directly proportional to its length, provided temperature and other physical conditions remain unchanged.

It means that R ∝ l i.e., if the length increases, the resistance also increases and if length decreases, its resistance also decreases.

(ii) Resistance of a conductor is inversely proportional to its area of cross section, other conditions remaining the same.

If A is the area of cross section, then :

R α 1/A

Or R α 1/πr2 where r is radius of the wire

Keeping the length same, if the radius of the wire is doubled then :

R α 1(2r)2 α 1/4r2

Or R α ¼.1/πr2, or R becomes one fourth.

Similarly if r is made half, then :

R α 1/(r/2)2

α 4/r2 α 4(1/r2), or R becomes 4 times

This shows that R is α 1/A

(iii) R depends on the nature of the material of the conductor. It means, if we take equal lengths of wires of copper, aluminium and iron and all of the same cross-sectional area, their resistance are different from each other since they are of different materials.

Explanation:

When an electric potential difference (V) is applied across a conductor as shown in the figure below, some current (I) flows through it. The flow of current is opposed by the resistance of the conductor and circuit. The relation between voltage, current and resistance is explained by the ohm’s law.

Ohm’s laws state that the current through any two points of the conductor is directly proportional to the potential difference applied across the conductor, provided physical conditions i.e. temperature, etc. do not change. It is measured in (Ω) ohm.

ohm-laws

Mathematically it is expressed as

ohms-law-1

In other words, Ohm’s law can also be stated as;

The ratio of the potential difference across the end point of the conductor to the current flowing between them is always constant, but the physical conditions of the conductor i.e. temperature, etc. remain same.

This constant is also called the resistance (R) of the conductor (or circuit)

ohms-law-2

It can be written as

ohms-laws-3-

In a circuit, when current flows through a resistor, the potential difference across the resistor is known as voltage drops across it, i.e., V = IR.