Each of the resistors shown in figure has a resistance of 10 Ω and each of the batteries has an emf of 10 V. Find the currents through the resistors a and b in the two circuits.
1A,0A,1A,0A
Given, resistance of resistor,
emf of each cell, 
A Equivalent circuits are
For current through a is 
As for b, the two emf cancel each other, thus total potential is zero. Hence, the current is zero.
B Equivalent circuits are
For current through a is 
Again for b, the two emf cancel each other, thus total potential is zero. Hence, the current is zero.
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