Straight wire: concentric circular field lines around the wire. Circular coil: field concentrated through the centre with return lines outside. Solenoid: near-uniform strong internal field with weaker external return field. [4]
The field pattern has a north and south end with closed field loops like a bar magnet; current direction sets the polarity. [3]
Reversing current reverses the field direction, so the north and south poles interchange. [2]
Q2 Two-Wire Superposition
At the midpoint, fields from equal same-direction currents are equal and opposite, so resultant is approximately zero. [2]
Outside the pair, fields are in the same direction locally and reinforce. [2]
It has magnitude and direction, and resultant fields must be found by vector addition. [2]