piece of plastic tape coated with iron oxide and is magnetised more in some parts than in others. When the tape is moved past as a small coil of wire (head of the tape recorder), the magnetic field produced by the tape changes, which leads to generation of current in the small coil of wire.

• How could we use the principle of electromagnetic induction in the case of using ATM card when its magnetic strip is swiped through a scanner? Discuss with your friends and your teacher.

• An induction stove works on the principle of electromagnetic induction. A metal coil is kept just beneath the cooling surface. It carries alternating current (AC) so that AC produces an alternating magnetic field. When you keep a metal pan with water on it, the varying magnetic field beneath it crosses the bottom surface of the pan and an EMF is induced in it. Because the pan is metal the induced EMF generates an induced current in it. Since the pan has a finite resistance, the flow induced current in it produces heat in it and this heat is conducted to the water. That’s why we call this stove as induction stove. Have you ever thought, from where do we get electrical energy? Let us learn about it.

  Electric Generator and Alternating - Direct Currents

• What happens when a coil is continuously rotated in a uniform magnetic field?

• Does it help us to generate electric current? Let us see:
  
  Consider a rectangular coil. Let it be held between the poles of Curve- shaped permanent magnet as shown in figure 17(a). As the coil rotates, the magnetic flux passing through the coil changes. According to the law of electro magnetic induction an induced current is generated in the coil.
  
  
• the direction of current induced in the coil constant? Does it change?
  
  
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