Question

state ohms law and write the condition under which it is valid

Answer 1

According to Ohm's law : 
At constant temperature the current flowing through a conductor is directly proportional to the potential difference across its ends.

If I is the current flowing through a conductor and V is a potential difference or voltage across it ends then according to Ohm's law:

I ∝ V 

[At constant temperature]

V ∝ I 

V = R × I

Where R is a constant called resistance of the conductor.
The value of this constant depends on the nature ,length ,area of cross section and temperature of the conductor.

V/I = R 

Here,

V = potential difference
I= current
R= resistance (which is a constant)

I = V/R

From this relation

1.The current is directly proportional to potential difference.

2. The current is inversely proportional to resistance.

If the potential difference across the ends of a conductor is doubled the current flowing through it also gets doubled and if the potential difference is Halved the current also gets halved.

If the resistance is doubled the current gets halved and if the resistance is Halved the current gets the doubled.

The SI unit of resistance is Ohm which is donated by the symbol Omega(Ω)

1 ohm is the resistance of a conductor such that when a potential difference of 1 volt is applied to its ends a current of 1 ampere flows through it.

The necessary condition for Ohm’s law to be applicable is that temperature must be constant.

hope it helps
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