CLASS 7 - ELECTRIC CURRENT AND ITS EFFECTS

ELECTRIC CURRENT AND ELECTRIC CIRCUIT

When you press the switch on, blub starts glowing. Why you think the bulb glows on putting the switch on?

When the bulb is on it get heated up and it produce light also. It means there is heat and light energy present in the bulb.

From where does this energy come?

According to the Law of Conservation of Energy: Energy can neither be created, nor be destroyed. But it can only be converted from one form to another.

Electric current: Electric current is defined as the rate of flow of negative charges of the conductor. In other words, the continuous flow of electrons in an electric circuit is called an electric current.

An electric current has electrical energy and this energy gets converted into light and heat energy when current flows through an electric bulb.

Electrons being negatively charged flow from the negative terminal to the positive terminal of the voltage source(battery). So, the current flow is considered in the direction opposite to the direction of flow of electrons.

ELECTRIC CIRCUIT: The arrangement where an electric current flows in a conductor when it is connected to a source of electric current.

COMPONENTS OF AN ELECTRIC CIRCUIT:

1. The cell or battery: Cell - Cell is a source of electric current. It has positive and negative terminal. In our daily life we use cell in many appliances like remote, alarm clocks, torch, mobile phone etc.

2. Battery: Combination of two or more cells is known as a battery. When the positive terminal of first cell is connected to the negative terminal of the second cell and so on.

2. SWITCH: Switch is an electrical component which can make or break electrical circuit automatically or manually. Switch is mainly works with ON (open) and OFF (closed) mechanism.

OPEN CIRCUIT: An open circuit is a circuit where the path has been interrupted or "opened" at some point so that current will not flow. An open circuit is also called an incomplete circuit.

CLOSED CIRCUIT: A closed circuit is any circuit that presents a complete path for the flow of electric current. An closed circuit is also called an complete circuit.

Switch is a device which is used to open or close the circuit. When switch is on the circuit is complete and current flows through the circuit and bulb glows. When switch is off the circuit is broken and current does not flow through the circuit and bulb will not glow.

3. Bulb: A light bulb is a device that produces light from electricity. Light bulbs turn the electricity to light by sending current through a thin wire called filament. The filament is usually made of tungsten, a material that emits light when electricity is passed through it.

4. Connecting Wires: A wire is a flexible strand of metal, usually cylindrical. Wires are used for establishing electrical conductivity between two devices of an electrical circuit.They possess negligible resistance(It is a measure of the opposition to current flow in an electric circuit) to the passage of current. The wires are covered by an insulated coating of different colours. The colour codes are used to distinguish between neutral and ground, and live wire, which differs from one country to another.

Electric circuit consists bulb, conducting wires, switch, cell or battery.

Symbols used to draw circuit diagram:

Bulb

Connecting wire

Cell

Battery

Switch

CIRCUIT DIAGRAM