A solenoid is a coil of wire whose turns combine their magnetic fields. Its external pattern resembles a bar magnet and the internal field is strong and approximately uniform away from the ends. A larger current, more turns per unit length or an iron core increases field strength; reverse the current to reverse the poles. Example: Describe the external pattern. Similar to a bar magnet. Distinguish the observation from the explanation, and support any judgement with evidence. Justify your answer.