Electric Currents and Circuits of Class 7

The simple step to make a magnate is flow electric current through a wire spiral around an iron bar then the bar behaves like a magnet.This type of magnet is known as electromagnet. When electric current flow in the wire then electromagnet is formed due to the magnetic effect of electric current. Hans Christian Oersted was the first person who discovered magnetic effect of electric current.We know that most of the invention we get accidentally as Hans was preparing for his lecture in this process he noticed that needle of the magnatic campas deflected when it was put near a wire that was connected to a battery.Every time the battery switched on or off deflection in the compass messured.

Construction of an Electromagnet

To construction of electromagnet we required

  • Two pieces of insulated copper wire
  • A nail
  • A battery containing two cells
  • A bulb with a holder
  • some paper clips made of iron.
  • Step first - Without any overlap wind a copper wire around the nail.
  • Step second –After removing the insulation on the wire at the two ends then connect one end of the wire to the battery and the other to one terminal of the bulb holder. Complete the circuit to connect one end of the second wire to the remaining terminal of the bulb holder, and the other end to the battery.
  • Step third- Place the paper clips near the nail.

When we switch on the battery then flow of current starts, the paper clips will cling to the nail. This is because the nail becomes an electromagnet. When the battery is disconnected, the nail is no more an electromagnet. The paper clips will not cling to the nail.

Application of Electromagnet

Electromagnets are used in

  • Electric bell.
  • Toys,
  • Separating iron from scrap in industries
  • Medicines
  • Cranes are used for lifting material
  • Iron industries
  • Electromagnetic trains called Maglev’s.

Construction and Working of an Electric Bell Circuit

construction of electric bell we required

  • An iron core that is used as the base in this spiral a wire as a coil.
  • A battery
  • A steel rod


When the switch ‘on’ electric current flows through the coil then the iron core (the base of the electric bell) acts as an electromagnet by this process .When this become a magnet its core attracts the hammer towards it.The hammer hits the bell and produces a sound.The circuit breaks at the screw contact when the hammer moves towards the iron core. At this point, the iron core ceases to be an electromagnet.The hammer is pulled back to its original position due to the spring action of the steel rod, and then touches the contact again to complete the circuit.The circuit is completed and current flows through the coil again, and the hammer strikes the bell again.The process repeats itself and we hear a ringing sound since the hammer keeps hitting the bell, until the switch is released.


electromagnet revision

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