Magnetic Effect of Electric Current:-
In 1820, Danish scientist Hans Christian Ørsted discovered that an electric current produces a magnetic field around a conductor. This discovery established the relationship between electricity and magnetism.
Activity 4.1: Oersted's Experiment
Aim:
To show that an electric current produces a magnetic field.
Materials Required:
•Battery (cell)
•Switch (key)
•Straight copper wire
•Connecting wires
•Magnetic compass
Procedure:
1.Place a magnetic compass on a table.
2.Keep a straight copper wire just above the compass needle in the north-south direction.
3.Connect the wire to a battery through a switch.
4.Close the switch to allow current to flow.
5.Observe the compass needle.
6.Open the switch and observe again.
7.Reverse the battery connections and repeat the experiment.
Observation:-
• When the switch is OFF, the compass needle points in the north-south direction.
• When the switch is ON, the compass needle deflects.
• When the direction of current is reversed, the compass needle deflects in the opposite direction.
Conclusion:-
• A current-carrying wire produces a magnetic field around it.
• The direction of the magnetic field depends on the direction of current.
Electromagnets:-
What is an Electromagnet?
An electromagnet is a temporary magnet produced when electric current flows through a coil of wire, usually wound around a soft iron core. It acts as a magnet only while current flows.
Activity 4.2: Making an Electromagnet
Aim
To make an electromagnet using a coil and an iron nail.
Materials Required:
Soft iron nail
Insulated copper wire
Battery (cell)
Switch
Paper clips or iron pins
Procedure:
1.Wind insulated copper wire tightly around the soft iron nail to form a coil.
2.Connect the ends of the wire to a battery through a switch.
3.Bring the nail near paper clips or iron pins.
4.Open the switch and observe.
Observation:
When the switch is ON, the nail attracts paper clips.
When the switch is OFF, the paper clips fall.
Conclusion:
A soft iron core becomes magnetic only when electric current flows through the coil.
Activity 4.3: Increasing the Strength of an Electromagnet
Aim
To study how the strength of an electromagnet changes.
Procedure
Prepare electromagnets with:
Different numbers of turns in the coil.
Different numbers of cells (higher current).
Count how many paper clips each electromagnet can lift.
Observation
More turns of the coil → Stronger electromagnet.
More current (more cells) → Stronger electromagnet.
Conclusion
The strength of an electromagnet increases by:
Increasing the number of coil turns.
Increasing the electric current.
Using a soft iron core.
Activity 4.4: Finding the Poles of an Electromagnet
Aim
To identify the north and south poles of an electromagnet.
Procedure
1.Connect the electromagnet to a battery.
2.Bring a magnetic compass near each end of the iron core.
3.Observe which end behaves as the North Pole and which as the South Pole.
4.Reverse the battery connections and observe again.
Observation
One end behaves as the North Pole, and the other as the South Pole.
Reversing the current reverses the poles.
Conclusion
The poles of an electromagnet depend on the direction of electric current.
Uses of Electromagnets
- Electric bells
- Cranes for lifting scrap iron
- Loudspeakers
- Relays
- Electric motors
- Magnetic door locks
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