Key Points

When an electric current flows through a conductor, such as a wire, it produces a magnetic field around the conductor. This phenomenon is known as the magnetic effect of electric current, discovered by Hans Christian Oersted.

A magnetic field is the region around a magnet or a current-carrying wire where its magnetic force can be detected. The presence and direction of a magnetic field can be observed by the deflection of a magnetic compass needle.

An electromagnet is a temporary magnet created by passing an electric current through a coil of insulated wire. The coil behaves like a magnet only when the current is flowing and loses its magnetism when the current is switched off.

The strength of an electromagnet can be increased by: (1) increasing the amount of electric current, (2) increasing the number of turns in the coil, or (3) inserting an iron core inside the coil.

Like a permanent magnet, an electromagnet has a North pole and a South pole. The polarity of the poles can be reversed by simply reversing the direction of the electric current flowing through the coil.

Electromagnets are used in many devices due to their controllable magnetic field. Common applications include electric bells, motors, loudspeakers, and large lifting electromagnets used in scrap yards to move heavy iron objects.

When an electric current passes through a conductor, the conductor gets heated. This is called the heating effect of electric current, which occurs because the conductor offers resistance to the flow of current, converting electrical energy into heat energy.

The amount of heat generated in a wire depends on its material, length, and thickness, as well as the magnitude of the current flowing through it. Wires made of materials with high resistance, like nichrome, produce more heat.

The heating effect is utilized in many household appliances that contain a heating element. Examples include electric heaters, electric irons, water heaters (immersion rods), electric kettles, and hair dryers.

An electric cell generates electricity through chemical reactions. A simple cell, like a Voltaic cell, consists of two different metal plates called electrodes, which are immersed in a chemical solution called an electrolyte.

A Voltaic cell uses two different metals as electrodes (e.g., a copper plate and a zinc plate) and a liquid electrolyte (e.g., a weak acid or salt solution). The chemical reaction between the electrodes and electrolyte produces an electric current.

A dry cell is a common portable power source where the electrolyte is a moist paste instead of a liquid. It typically has a zinc container that acts as the negative terminal and a central carbon rod with a metal cap as the positive terminal.

Rechargeable batteries can be used multiple times by reversing the chemical reaction using an external power source. They are commonly used in devices like mobile phones, laptops, and electric vehicles, reducing waste compared to single-use cells.