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Physics

Arrangement of Resistors and Ohm’s Law

Resistors can be arranged in series and in parallel.

resistor-series-parallel

have different potential differences.

When they are connected in parallel, they have the same potential difference but different current.

Ohm’s Law

The electric current passing through a metallic conductor is directly proportional to the potential difference applied between its end provided temperature and other physical property of the conductor remains constant.

Current =Potential differenceResistanceV=IR

R is a constant of proportionality and depends on the nature of the material. The unit of resistance is ohm.

Calculations

  1. A potential difference of 240V is applied to a lamp of 60 ohms resistance. What amount of current will flow in the circuit?

Solution

Current =Potential differenceResistance=24060=4A

  1. (a) Calculate the effective resistance in the diagram shown below. circuit example(b) Calculate the current flowing in the circuit aboveSolution(a) Solve the parallel first,1RP=1R1+1R21RP=12+121RP=22=1RP=1ΩR=RP+4=1+4=5Ω(b) Total resistance = 5Ω.From Ohm’s law,Current =Potential differenceResistance=205=4A
    1. A current of 3A flows in a circuit when a p.d of 24V is applied to it. The resistance across the circuit is
    SolutionI=3AV=24VR=?V=IR24=3×RR=243=8Ω

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