Question

You short-circuit a 12 volt battery by connecting a short wire from one end of the battery to the other end. If the current in the short circuit is measured to be 17 amperes, what is the internal resistance of the battery

Answer 1

0.7Ω

Step-by-step explanation:

Data

The electromotive force(emp)is 12 volts.

The short circuit current is 17 amperes.

The internal resistance is unknown.

In short circuit definitely the external resistance is Zero, we can find the internal resistance because of short circuit current.

`(emp-rI_(sc) )-RI=0`

• r is internal resistance of the battery which find the maximum current that can be out of the battery.

• R is external resistance R=0
• 
  `I_(sc)` is short circuit current

when take R=0

`(emp-rI_(sc) )-(0)I=0\\(emp-rI_(sc) )-0=0\\emp=rI_(sc)`

divide both side by
`I_(sc)` to find r

`r=(Emp)/(I_(sc) )`

now substitute the values

`r=(12V)/(17A) \\`

`r=0.7`Ω

The internal resistance of the battery is 0.7Ω

Answer 2

The internal resistance of the battery is 9.705 Ω

Step-by-step explanation:

The total resistance of the circuit is

Req = R + r

=(9 + 0.705) Ω

= 9.705 Ω