A cell can supply currents of 0.60 A and 0.30 A through a 2.0 ω and a 5.0 ω resistor respectively. What is the internal resistance of the cell?

VTPETERS2002

5 years ago

E=I(R + r) lets form a simultaneous equation:

E=?, I=0.60A, R=2ohms, r=?
E=0.6(2 + r)
E=1.2 + 0.6r---------(i)

for the second equation,
E=?, I=0.30A, R=5ohms, r=?
E=0.30(5 + r)
E=1.5 + 0.30r---------(ii)

combine (i) with (ii)
E=1.2 + 0.6r E=1.5 + 0.3r
To eliminate E, multiply (ii) by -1:
Add (i) to (ii)
(E=1.2 + 0.6r) + (-E= -1.5 - 0.3r)
0= -0.3 + 0.3r
0.3r= 0.3
r=0.3/0.3
r=1ohm

rc12

1 year ago

that is why it is a neco question. solve yours uaing a short method