Question

when a 12 V battery is connected across an unknown resistor, there is a current of 2.5mA in the circuit. Find the value of resistance of resistor.

Answer 1

v=ir
12=((2.5)/1000)*r
r=120000/25
...
solve.

Answer 2

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$\: \: \fcolorbox{red}{yellow}{ > > HOLLA! \: MATE < < } \\ \\ \: \: \: \: \: \underline{ \underline \blue {\boxed { \star \: \mathbb{Here \: Is \: Your \: Answer \: \star}} } }$
>> we have 12 v of battery and i =2.5MA
>> firstly convert the MA into only Ampere so,
>> Milliampere = 1/1000 ampere
>>2.5milliampere =2.5/1000=0.0025 ampere

$as \: we \: knows \: that \\ \huge \: \mathcal{i = \frac{V}{R} \: } \\ \mathfrak{ > > 0.0025 = \frac{12}{R} \:, \: R \: = \frac{12}{0.0025} } \\ \frak{ \: R = \: 4,800 }$