Have you seen a bolt of lightning before a thunderstorm on rainy days? Did your elders tell you not to touch electronic devices with wet hands? You must have seen electronic appliances like a television, refrigerator, air conditioner, and mixer at your home. Do they work automatically? Or do they need some energy to work? Yes. This energy is known as electricity. The above example of the bolt of lightning is also electricity. When we touch electronic devices with wet hands, we may get shocked due to the electric supply. This is why we should not touch electronic appliances with wet hands. These are all examples of electricity. In simple words, electricity means the movement of electrons from one point to another point in a conductor.
These are materials that allow an electric current to pass through them.
Examples: Metals, Saltwater.
In conductors, the atoms are tightly bound to each other. The atoms are composed of protons, neutrons, and electrons. The protons and neutrons are located in the centre of the atom. The centre of the atom is known as the nucleus. The electrons revolve around the nucleus. The electrons present in the outermost shell are loosely held to the atoms. They carry electric current and move freely from one atom to another atom. Hence, metals are good conductors of electricity.
These are materials that do not allow an electric current to pass through them.
Examples: Rubber, Plastic, Glass.
In insulators, the electrons present in atoms are also tightly bound to each other. But they cannot move freely on the application of electricity. Hence, insulators cannot conduct electric current. They are also called bad conductors of electricity.
It mainly consists of the following components:
Electric cells: They mainly provide electricity. It is commonly known as battery cells. It is present in clocks, transistors, etc. The electric cells have two terminals. They have a metal cap on one side and a metal disc on another side. Metal caps have a positive terminal, and metal discs have a negative terminal. The electricity is produced by the cells due to the storage of chemicals in it.
Bulbs: In an electric circuit, the glow of the bulbs shows the presence of an electric supply. The bulbs glow if there is an electric supply in a circuit. Bulbs do not glow if there is no electric supply in a circuit.
Switches: It is used to light electric bulbs and other devices.
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Let us understand some basic terms used to study electricity.
An electric current consists of electrons flowing through a conductor at a certain rate. It is denoted by 'I'. Electric current is expressed in Ampere.
$$\mathrm{1\:ampere=\frac{1\:Coulomb}{1\:second}}$$
A charge is a property of subatomic particles such as protons and electrons. In an electric field, it helps to experience a force. It is expressed in Coulomb.
It is the difference in potential between two points in an electrical circuit. It is denoted by 'V'. It is expressed in volt.
$$\mathrm{Potential\:difference \:(V)=\frac{Work\:done\:(W)}{Charge\:(C)}}$$
It is the force that makes the electrons move in a certain direction. It is expressed in Volt.
It is the opposition to flow of electrons in a conductor. It is expressed in ohm. Insulators like glass and rubber show higher resistance. The low resistance is shown by metals like silver, copper, etc.
It states that the current in a conductor is proportional to the potential difference when the temperature and physical conditions of the conductor remain constant.
$$\mathrm{Resistance\:(R)=\frac{Potential \:difference(V)}{Current\:(I)}}$$
In this effect, a conductor generates heat when an electric current travels through it.
The equation for the heating effect of electric current is given by, ${H=I^2RT}$
where H = Heat
I = Amount of current
R = Resistance in conductor
T = Time for which the current flows
The heating effect of electric current is mainly applied in electronic appliances It includes electric kettles, electric heaters, electric laundry iron, oven, and toaster.
Have you put a compass near a wire carrying a strong current? If yes, then you must have observed the needle of the compass deflects. It is due to the magnetic effect produced by electric current.
The ionic solution is broken down into ions by passing an electric current through it. The chemical effects are observed in solution. They include the release of bubbles and a change in the colour of the solution.
Direct current: The flow of electrons from a region of higher density to a region of lower density is called a direct current. It has applications in household electronic appliances. The direction of this current remains the same.
Alternating current: It keeps changing its direction hence it is known as alternating current.
Electricity was discovered in 600 Before Christ (B.C.)
It travels at the speed of light i.e. $\mathrm{3\times 10^{8}m/s}$
The electronic appliances plugged into the switches use energy even if they are switched off. So, we should plug off the appliances when we don't use them.
Copper is used in electric wires in industry.
Electricity is the flow of electrons from one point to another point in a conductor. A conductor carries a current while an insulator does not carry current. Heat, magnets, and chemicals have an effect on electric current
Q1. Which metals do not conduct electricity?
Ans. Bismuth and tungsten have high resistivity than any other metals. Hence, they do not conduct electricity.
Q2. Name a device that helps to maintain a potential difference across a conductor.
Ans. A device like cells or battery maintains potential difference across a conductor.
Q3. How much energy is given to each coulomb of charge passing through a 6 V battery?
Ans. The potential difference between two points is given by the equation,
V= W/Q, where,
W is the work done in moving the charge from one point to another
Q is the charge From the above equation, we can find the energy given to each coulomb as follows: W= V x Q
Substituting the values in the equation, we get
${W = 6V\times 1C=6\:J}$
Hence, 6 J of energy is given to each coulomb of charge passing through a 6 V of battery.
Q4. Why are coils of electric toasters and electric irons made of an alloy rather than a pure metal?
Ans. Alloys have a higher melting point than a pure metal due to their high resistivity. Alloys do not melt easily at high temperatures. Hence, the coils of electric toasters and electric irons are made of an alloy.
Q5. On what factors does the resistance of a conductor depend?
Ans.
Length of conductor
Temperature of conductor
Nature of material of the conductor
The Cross-sectional area of conductor
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