A 'black box' contains N identical non-ideal cells connected in parallel. The terminal voltage V of the box versus the current I drawn from it is plotted, yielding a straight line. The y -intercept (open-circuit voltage) of this graph is 12 V and the x -intercept (short-circuit current) is 24 A . If the short-circuit current of a single isolated cell from the box is 3 A , what is the number of cells N and the interna

Step-by-step solution

The y -intercept of the V-I graph represents the open-circuit voltage, which is the equivalent EMF of the parallel combination. For N identical cells in parallel, the equivalent EMF is equal to the EMF of a single cell. Thus, E_ eq = E = 12 V . The short-circuit current of a single isolated cell is given as 3 A . E r = 3 A 12 r = 3 r = 4 The x -intercept of the V-I graph represents the short-circuit current of the entire black box, which is 24 A . The equivalent internal resistance of N cells in parallel is r_ eq =