Current Electricity and Electrical InstrumentHard

Question

A current of 2 A flows through 2Ω resistor when connected across a batery. The same battery supplies current of 0.5 A when connected acros a 9Ω resistor. The internal resistance of the battery is

Options

A.0.5 Ω
B.1/3 Ω
C.1/4 Ω
D.1 Ω

Solution

Let ε be the emf and r be internal resistance of the batteryIn first case
     
         ...... (i)
  In second case
     
         ...... (ii)
  Divide (i) by (ii)
            ⇒ 4 + 2 r = 4.5 + 0.5 r
     1.5 r = 0.5       ⇒ r =

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