Three resistors of 10 Ω, 15 Ω and 20 Ω are connected in series in a circuit. If the potential drop across the 15 Ω resistor is 3 V, find the current in the circuit and potential drop across the 10 Ω resistor.



According to ohm’s law,

           V= IR


  • V is potential difference.
  • I is current.
  • R is resistance.

   Current through 15 ohm resistor with potential difference 3 V, 

I = V / R

   = 3 / 15

   = 0.2 A

In a series circuit, the same current flows through the entire circuit.

Therefore, current in the circuit = 0.2 A

Potential drop across the 10 ohm resistor,

V = I*R

   = 0.2 A * 10 ohm

    = 2 V 

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CA Maninder Singh is a Chartered Accountant for the past 13 years and a teacher from the past 17 years. He teaches Science, Economics, Accounting and English at Teachoo