Question

You take a lab battery and, when it isn't connected to a circuit, you measure a voltage of 4.00-V with a voltmeter. You then connect the battery to a 200-12 resistor and measure a current of 17.5-mA. What is the internal resistor of this battery?

Answer 1

`r = 28.6 ohm`

Step-by-step explanation:

As we know that when battery is in open circuit then the potential difference of the cell is known as EMF

so EMF is given as

`EMF = 4.00 V`

now when the battery is connected across a resistance of 200 ohm then there is current flowing through the battery

it is given as

`i = (V)/(R + r)`

`17.5 * 10^(-3) = (4)/(200 + r)`

`200 + r = 228.6`

`r = 28.6 ohm`