Question

Figure shows a circuit diagram containing 12 cells, each of e.m.f 1.5V and intenal resistance 0.25Ω Calculate:

(a) Total internal resistance 

(b) Total e.m.f. 

(c) Total external resistance 

(d) Reading shown by the ammeter 

(e) Current in 12Ω and 8Ω resistors 

(f) p.d. across 2.2 resistor 

(g) Drop in potential across the terminals of the cell

Answer 1

Number cells in series = n = 12 

(a) Total internal resistance of 12 cells = n r = 12 × 0.25 = 3Ω 

(b) Total e.m.f. = 12 x 1.5 = 18v 

(c) Total external resistance : 4 + 8 = 12Ω in series