Wait, so if a question talks about doubling the current how am I meant to know the effect on the field?
Also, I came across a question involving two parallel current carrying wires, where the distance between them was reduced by a factor of 2, In the answers it said field varies inversely with distance squared. Again how am I meant to know this?
The awkward bit is...your answers are wrong. For parallel current carrying wires, the field strength is inversely proportional to the distance from the wire. I don't want to prove this here as 1. I would have to do some messy integration, or 2. I would have to introduce another physical law which would make no sense here.
You don't needed to know anything about magnetic field strengths in VCE, although maybe you need to know that increasing the distance generally decreases field strength (but not how).
That logic. We're taught that currents create a magnetic field, that increasing currents create larger magnetic fields and how magnetic forces operate, but we're not taught how to calculate magnetic field strengths. VCAA logic.