What shape is Earth's magnetic field?
Take a long wire and wind it around a pencil, loop after loop, into a tight coil of many turns. Slide the pencil out, switch on a current, and sprinkle iron filings around the coil. The filings draw a familiar picture: the pattern of a bar magnet.
A wire wound into a coil of many turns is called a solenoid. Here is what winding the wire does to its field, one step at a time.
The solenoid's field lines leave one end, loop around outside, and return to the other end. So the solenoid has a north pole at one end and a south pole at the other, just like a bar magnet.
The straight wire's circles have not gone away. Winding the wire stacks each turn's circles into one bar-magnet-shaped field.
A current flows through a wire coil of many turns. What shape is the coil's field?
Where are a current-carrying solenoid's magnetic poles?
One end of a current-carrying solenoid attracts the south end of a compass needle. What is that end of the solenoid?
A solenoid has a north pole at one end and a south pole at the other.
Unlike poles attract, so a south end is attracted to a north pole.
That end of the solenoid is a north pole.
A compass is carried around the outside of a current-carrying solenoid, always following the field. Which pattern does the needle trace out?
Outside, the solenoid's field is shaped like a bar magnet's.
The field lines loop from one end of the solenoid around to the other.
The needle traces a bar-magnet-style loop from one end of the solenoid to the other.
What is a wire wound into a coil of many turns called?
Which statement about a current-carrying solenoid is correct?
One end of a current-carrying solenoid repels the north end of a compass needle. What is that end of the solenoid?
The current through a solenoid is switched off. What happens to its field?