Question 1 What are conductors? Give examples?
Question 2 What are insulators? Give examples?
Question 3 State few uses of conductors and insulators?
Question 4 Why should we wear rubber soled shoes or rubber chappals while operating electrical appliances?
Question 5 Why it is advisable to operate electric switches with dry hands?
Question 6 Why do electricians wear rubber hand gloves while working with electricity?
Question 7 The handles of tools screwdrivers and pliers used by electrician for repair work usually have plastic or rubber cover on them. Explain?
Also Read NCERT Solutions for Chapter 12 Electricity and Circuits
Some materials allow electric current to pass through them whereas other materials do not allow an electric current to pass through them.
Conductors
Those materials which allow electric current to pass through them are called conductors. The flow of electric current is called electricity. All the metals are conductors of electricity. Silver metal is the best conductor of electricity. Copper and aluminium metals are also good conductors. Electric wires are made of copper and aluminium because they are conductors of electricity.
For example : iron, steel, mercury, gold, metal alloys (like Steel, brass, bronze) are conductors of electricity. All the objects made of metals or metal alloys are also conductors. The objects such as coins, keys, pins, aluminium foil, sewing needles and iron nail are all conductors of electricity.
A non-metal called carbon (in the form of graphite) is also a conductor of electricity. The thin black core of our pencil is called pencil lead which is made of graphite and is also a conductor of electricity.
The human body conducts electricity to small extent as it is a poor conductor of electricity. A person gets electric shock on touching an uncovered electric wire carrying current because some electric current passes through his body.
Water is a poor conductor of electricity. If a person operates an electric switch with wet hands, he can get an electric shock because water present on the wet hands can conduct some electricity from the switch into his body. We should, therefore, operate the switches of electrical appliances with dry hands.
Insulators
Those materials which insulators do not allow electric current to pass through them as called insulators.
For example: rubber, plastic, ceramics, porcelain, asbestos, wood, glass, mica, cotton, jute, wax, paper, air etc.
Rubber is an insulator, therefore an eraser and balloon are also insulators. Wood is an insulator, so objects made of wood are also insulator. Plastic is an insulator, so plastic scale, polythene bags, nylon socks are also insulators. A candle, glass are insulators.
The outer covering of electric wire is made of plastic because plastic is an insulator. Plastic covering does not allow electric current to pass through it. When an electric switch is in the off position then air is present between the ends of wire connected to the switch. Since air is a non conductor of electricity, electricity is not conducted across the gap between the ends of the wire in the switch and hence the bulb does not light up.
Importance of Conductors and Insulators
For example : The electric wires are covered with insulators like plastic or rubber. Being an insulator, plastic (or rubber) covering does not conduct electricity flowing through the wire into our body when we touch it. So, if we happen to touch a current-carrying wire covered properly with plastic (or rubber) insulation, we will not get an electric shock. Thus, the plastic (or rubber) covering on the wires protects us from the electricity that is flowing through the wire. The plastic insulation makes the electric wires safe to touch.
Electric plugs, electric switches, electric plugs, electric sockets, electric iron, toaster and ovens, etc., are also covered with insulator material like plastic to protect us from the electricity passing through them
(1) Those parts of an electrical component or appliance through which electric current has to pass, are made of conductors like metals or metal alloys.
(2) Those parts of an electrical component or appliance which are touched by us while handling, are made of insulators like plastic, rubber or wood etc.
The electric wires are made of metals like copper and aluminium because they are conductors but the outer covering of electric wires is made of plastic (or rubber) because it is an insulator.
(1) The pins of an electric plug are made of metal which is a conductor but the outer case is made of plastic which is an insulator.
(2) The inner parts of electric switches and electric sockets are made of metal (conductor) but their outer case is made of plastic (insulator).
(3) The heating element of an electric iron is made of a metal alloy (which is a conductor) but heating element is enclosed in a sheet of mica which is an insulator.
(4) The handle and top part of an electric iron (which we touch) are made of plastic which is also an insulator.
Rubber, plastics and ceramics are often used to protect us from the dangers of electricity because they are good insulators.
For example :Electricians wear rubber hand gloves while handling naked electric wires because rubber is a good insulator and protects them from electric shocks.
The handles of tools like screwdrivers and pliers used by electricians for repair work usually have plastic or rubber covers on them. This is because plastic and rubber are insulators which protect the electrician from electric shocks when he is handling current-carrying electrical appliances. It is advisable to wear rubber-soled shoes or rubber chappals while operating electrical appliances. This is because rubber is an insulator which will protect us from electric shocks in case there is a leakage of electric current from the appliances.
| Notes for Chapter 12 Electricity and Circuits |
Very nice notes
Very nice
very helpful thankyou.
Notes are very nice but answer in short