Three cells of emf 2V,1.8V and 1.5V are connected in series.Their internal resistances are 0.05ohm, 0.7ohm and 1ohm respectively.If the battery is connected to an external resistor of 4ohm via a very low resistance of ammeter, what would be the reading in the ammeter?

Net current I = net emf/net resistance
  now net resistance =0.05+4+0.7+1=  5.75Ω   since all resistors are in series
   net emf =2+1.8+1.5 =5.3 V 
I = 5.3/5.75
  0.92 A
hence the current read by ammeter is 0.92 ampere

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