Concepts of Physics

IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

Play with solenoid pulling/pushing ferromagnetic materials-II


It is the same theory but the material to be used is ball bearing balls. These are ferromagnetic and can easily be magnetized. When the field is removed the balls get readily demagnetized.


A solenoid, variac connected to mains, ball bearing balls of different sizes, a dish

Variac: This is an instruments which gives AC of desired voltage from 0 to 230 V. you adjust the voltage by rotating its knob. In this experiment, you should not go beyond 30 V. That two for short periods like few seconds.


  1. Connect the variac terminals to the ends of the solenoid. Connect the variac to the mains but keep the switch of mains off.
  2. Take lots of small balls in a plastic box. Hold the box in one hand and put the solenoid vertically in the box. Push it down to the bottom of this plastic box. Keep your hands at a height so that you can see the bottom of the solenoid from below and the bottom remains horizontal.
  3. Now switch on the –—. What do you see of the balls?
  4. Place the solenoid vertically on the ground and put 8-10 balls of bigger size in it. All the balls will at the bottom randomly.
  5. Now switch on the mains AC power. What do you see of the balls?
  6. Keep 6-7 bigger balls in a dish. Hold the dish close to the upper end of the solenoid. Switch on the AC power. What do you see of the balls?