(a) Suppose that you connect two identical flashlight batteries in series to get
ID: 1443926 • Letter: #
Question
(a) Suppose that you connect two identical flashlight batteries in series to get a 3 V emf. Write a loop equation to show that the maximum (short-circuit) current these batteries can deliver is exactly the same as the maximum current from one battery.
(b) Alternatively, suppose that you connect two identical flashlight batteries in parallel, which gives you just a 1.5 V emf. Write loop and node equations to show that the maximum (short-circuit) current these batteries can deliver is double that of one battery.
Explanation / Answer
a)
Let internal resistance of each battery be r ohm
Emf of each battery = 1.5 V
current by each battery = 1.5/r
When 2 batteries are connected in series,
Total emf = 3 V
total resistance = 2*r
current = 3V/(2r) = 1.5/r
current is same as supplied by 1 battery
b)
Let internal resistance of each battery be r ohm
Emf of each battery = 1.5 V
current by each battery = 1.5/r
When in parallel each battery will give current = 1.5/r
Total current = 1.5/r + 1.5/r = (1.5+1.5)/r = 3/r
It is double of current produced by a battery
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