CBSE · Class 10 · Science · Magnetic Effects of Electric CurrentExplain the principle, construction, and working of an electric generator (AC generator). Draw a neat and labeled diagram to support your answer.

Principle of Electric Generator\nAn electric generator works on the principle of electromagnetic induction discovered by Michael Faraday. When a closed coil is rotated in a uniform magnetic field, an electric current is induced in the coil due to a continuous change in the magnetic flux linked with it. It converts mechanical energy into electrical energy.

Construction\nAn AC generator mainly consists of the following essential components:

• Armature (Coil): A large rectangular coil ABCD having a large number of turns of insulated copper wire wound over a soft iron core. It is capable of rotating rapidly about an axis between the poles of a magnet.
• Strong Field Magnet: A permanent magnet or an electromagnet with concave poles (North and South poles) that provides a strong, uniform magnetic field across the armature.
• Slip Rings: Two hollow metallic rings $R_1$ and $R_2$ to which the two ends of the armature coil are connected respectively. These rings rotate along with the rotation of the coil.
• Brushes: Two static carbon brushes $B_1$ and $B_2$ that gently press against the slip rings $R_1$ and $R_2$. These brushes remain stationary and maintain electrical contact with the rotating rings to transfer the generated current to the external circuit.
• External Circuit: Connected across the brushes to receive the output alternating current.

Working

1. Initial Rotation: Suppose the armature coil ABCD is initially in a horizontal position and is rotated clockwise manually or by a turbine.
2. First Half-Rotation: As the coil rotates, arm AB moves downward and arm CD moves upward. They cut the magnetic field lines. According to Fleming's Right-Hand Rule, an induced current flows along the path $ABCD$. Consequently, current flows through the external circuit from brush $B_2$ to $B_1$.
3. Second Half-Rotation: After half a revolution, arm AB comes to the right and CD comes to the left. Now, arm AB moves upward and CD moves downward. The direction of induced current reverses, flowing along $DCBA$. Thus, current in the external circuit flows from brush $B_1$ to $B_2$.
4. Alternating Nature: Since the direction of current changes after every half-rotation, the current produced is an alternating current (AC).