Take a wooden plank covered with white paper. Make equidistant holes on its surface as shown in figure 6(a). Pass copper wire through the holes as shown in figure 6(a). This forms a coil. Join the ends of the coil to a battery through a switch. Switch on the circuit. Current passes through the coil. Now sprinkle iron filings on the surface of the plank around the coil. Give a small jerk to it. An orderly pattern of iron filings is seen on the paper.
• How do they adjust in such an orderly pattern?
This long coil is called solenoid. A solenoid is a long wire wound in a close packed helix. The field of solenoid is shown in the figure 6(b). The magnetic field lines set up by solenoid resemble those of a bar magnet indicating that a solenoid behaves like a bar magnet. The direction of the field due to solenoid is also determined by using right hand rule. One end of the solenoid behaves like a north pole and other behaves like a south pole. The field lines outside the solenoid are continuous with those inside. Outside the solenoid the direction of the field lines is from north to south while inside the direction is from south to north. Thus the magnetic field lines are closed loops. This is so for the bar magnet too!
We have seen that current carrying wires produce magnetic field. So, electric charges in motion produce magnetic fields.
• What happens when a current carrying wire is kept in a magnetic field?
Magnetic Force On Moving Charge And Current Carying Wire
Take a bar magnet and bring it near the TV screen (The old CRT type TV). What do you observe?
You can observe that the picture on the screen is distorted.
Take a wooden plank covered with white paper. Make equidistant holes on its surface as shown in figure 6(a). Pass copper wire through the holes as shown in figure 6(a). This forms a coil. Join the ends of the coil to a battery through a switch. Switch on the circuit. Current passes through the coil. Now sprinkle iron filings on the surface of the plank around the coil. Give a small jerk to it. An orderly pattern of iron filings is seen on the paper.