The first problem you're given the total current that is going through the core, so you don't know how much of it is going through the core resistance and the core inductance but the voltage across both is the same and is equal to the input voltage Vtest. So naturally it's easier to use what is...
If the neutral lead is connected to the rectifier why is the charging current negative and the correct answer is not graph B?
Please see the attached photo for what I mean.
Any help is appreciated.