Electric conductors and insulators — lesson. Physics CBSE Live product, Class 7 (2025-26).

If wires are made from materials other than metals and used in an electrical circuit, it raises an important question about the flow of electric current. Electric current can pass only through materials that allow the movement of charges easily. Therefore, such materials may or may not allow current to flow depending on whether they are conductors or insulators.

Activity: To identify materials through which electric current can and cannot pass using a simple conduction tester.

Step 1: Connect an electric cell and a lamp using connecting wires, keeping the two free ends of the wires open.

Step 2: Touch the two free ends of the wires together momentarily to check whether the lamp glows. If it glows, the tester is ready.

Step 3: Collect objects made of different materials such as a metal spoon, coin, cork, rubber, glass, key, pin, plastic scale, wooden block, aluminium foil, candle, paper, and pencil lead.

Step 4: Touch the two free ends of the tester’s wires to the two ends of each object, one object at a time.

Step 5: Ensure that the wires do not touch each other directly.

Step 6: Observe whether the lamp glows for each object and record your observations in the table.

S.No.	Object	Material it is made of	Lamp glows? (Yes/No)	Conclusion
1.	Stick	Wood	No	Insulator
2.	Scale	Plastic	No	Insulator
3.	Key	Metal	Yes	Conductor
4.	Bangle	Glass	No	Insulator
5.	Eraser	Rubber	No	Insulator
6.	Paper strip	Paper	No	Insulator
7.	Candle	Wax	No	Insulator
8.	Coin	Metal	Yes	Conductor
9.	Aluminium foil	Metal	Yes	Conductor

Observation:

The lamp glows for some objects but does not glow for others.This shows that electric current passes through certain materials easily, while it does not pass through some materials.

Conclusion:

From this activity, we observe that the lamp glows only for some materials. This shows that electric current can pass through conductors, while it cannot pass through insulators.

Conductors:

Materials through which electric current can pass easily are called conductors or good conductors of electricity.

Example:

Copper, graphite, silver, gold, aluminium, steel, etc.

Copper, graphite and steel

Insulators:

Materials through which electric current cannot pass are called insulators or poor conductors of electricity.

Example:

Wood, plastic, rubber, glass, paper, etc.

Wood, rubber, paper and plastic

Electrical conductors used for making wires:

Silver, copper, and gold are among the best conductors of electricity. However, copper is most commonly used for making electrical wires because it is less expensive and easily available compared to silver and gold. Different types of electrical wires are used for different purposes depending on their application.

Why are electrical wires covered with insulators?

Materials such as plastic, rubber, and ceramics do not allow electric current to pass through them. These materials are electrical insulators. Covering electrical wires with insulators prevents the electric current from coming into direct contact with our body, ensuring safety.

Electrical wires with insulation

Uses of conductors and insulators:

Both conductors and insulators play an important role in electrical systems. Conductors are used to make electrical wires, switches, plug connectors, and sockets because they allow electric current to flow easily. Insulators like rubber, plastic, and ceramics are used to cover wires, plug tops, and switches to protect users from electric shock.

Plug tops

Caution: Electrical safety

The human body is a conductor of electricity. If electric current passes through our body, it can cause serious injury or even death. Therefore, always handle electrical appliances carefully. Never touch switches or plugs with wet hands, avoid using electrical devices in wet places, and do not use appliances with damaged wires or broken plugs.

Handling wires with safety equipments

Types of electric current: DC and AC

Have you ever thought about how electricity from a cell or battery differs from the electricity supplied through a wall socket? Electricity from cells and batteries is mainly used to operate small devices and is called Direct Current (DC). On the other hand, electricity supplied to wall sockets comes from power stations, is called Alternating Current (AC), and is used to run larger electrical appliances.

2. Electric conductors and insulators

Theory: