Class 10 Science

Electricity: Ohm's Law

These notes are based on the chapter Electricity class 10 science of NCERT book and CBSE syllabus.

  • Relation between potential difference and electric current
  • Resistance

This law explains the relationship between potential difference and electric current. Ohm's Law states that the potential difference between two points is directly proportional to the electric current. This means, potential difference V varies as electric current.

Or, `V∝I`

Or, `V/I=R`-----------(1)

Or, `1/I=R/V`

Or, `I=V/R`----------(2)

Or, `V=RI` ----------(3)

Where R is constant for the given conductor at a given temperature and called resistance. Resistance is the property of conductor which resists the flow of electric current through it.

SI Unit of resistance is ohm. Ohm is denoted by Greek letter Ω.

1 ohm (Ω) of Resistance (R) is equal to the flow of 1 A of current through a conductor between two points having potential difference equal to 1 V.

This means `1Ω=(1V)/(1A)`

From the expression of Ohm’s Law it is obvious that electric current through a resistor is inversely proportional to resistance. This means electric current will decrease with increase in resistance and vice versa.

The graph of V (potential difference) versus I (electric current) is always a straight line, with and upward slant.

potential differnce electric current graph

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