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Electricity can be defined as a phenomenon that can be associated with stationary or moving electric charges from one matter to the other. The S.I. unit of electricity is Watt. A Watt can be described as the amount of electricity equivalent to one joule per second. Electricity the the core source of energy that are used in daily lives from regular life to the medical field.
Key Terms- Electric current, Electricity, Ohms Law, Electric energy, Coulomb, Ampere, Electrostatics.
What is Electricity?
According to Merrium-Webster dictionary Electricity can be defined as, “ a fundamental form of energy observable in positive and negative forms that occurs naturally (as in lightning) or is produced (as in a generator) and that is expressed in terms of the movement and interaction of electrons”. Electricity is a form of energy that can be observed in positive and negative forms, either in a natural form like lightning or produced like a generator. It is an fundamental property of any matter.
- The charge is a scalar quantity because it is only a magnitude and has no direction.
- The charge can be positive or negative.
- The charge cannot create or destroy charges.
- Per Coulomb contains about 6 x 1018 electrons.
Electricity Flow
Electric Current
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An electric current is when a stream of charged particles like ions move through space.
Ampere is the common unit of electric current. It is defined as a flow of a single coulomb of charges per second. In numerical terms, it is determined as 6.2 × 1018 electrons per second.
1 ampere = 3 × 109 esu per second.
esu= electrostatic unit of charge
Coulomb is abbreviated as C.
Heating Effect of Electric Current
When an electric current is passed through a current it gets hot and produces heat, this is due to the conversion of electric energy to heat energy. This is called the heating effect of electric current.
- Electrical laundry iron, toaster, heater, electrical bulb and fuses can be considered as a few examples of the heating effect of electric current.
- The heating effect of electricity can be represented as H = I2 Rt, where I repesent electric current, R represent conductor of resistance, t represents time.
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Electric Charge
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Electric charge is a property of matter which causes it to experience force. Is that property that causes objectives to feel an attractive pull or a repulsive force towards one another. There are two types of charges, they are positive and negative. Coulomb's Law states that while the like charges repel, the unlike charges will attract. It shows how strong the push or pull force is between two points of charge. The electric charge is the amount of charge flowing at a particular time through a particular area.
Here are few related units of measuring electric charges-
- Watt- Watt is the measurement used to measure electricity in units of power. Watt is equal to one joule per second.
-
Kilowatt-hour- It is the commercial unit of electrical energy generally billed to consumers. 1 kilowatt hour = 1,000 watts.
Here are a few instruments that helps in measuring electric charges-
| Instruments | Decriptions |
|---|---|
| Galvanometer | A galvanometer is an electromechanical instrument used to measure small electric current or their voltage. It was one of the first instruments used to detect the flow of an electric current. |
| Ammeter | An ammeter is another device to measure direct or alternating electric current in a circuit. Here, the electric currents are measured in amperes(A). The different types of ammeter are AC ammeter, DC ammeter, Permanent moving coil ammeter, Moving iron ammeter, Electro-dynamometer ammeter, and Rectifier type ammeter. |
| Voltmeter | A voltmeter is a device that is used to measure the potential difference between two points in an electric circuit. It has high resistance and usually measures voltages in either direct or alternating current on a scale of volts, millivolts, or kilovolts. |
| Conductors | Those materials that allow the flow of electricity are conductors. This is because electrons flow easily from atom to atom. They have free electrons on the surface which allow free transmission of electricity. Conductors allow the transmission of heat or light from one material to another. Some examples of conductors are Metal, Earth, the Human body, mercury is a liquid conductor. |
| Insulators | These are materials that do not allow the flow of electricity between them. This is because the atoms are quite far apart from each other. Such materials do not pass the flow of heat or electricity through them. Some examples of insulators are Glass, Rubber, Plastic, and so on. |
| Semiconductor | These are those materials whose electrical conductivity falls between that of a conductor or insulator. Some examples are Silicon, Germanium, etc. |
Electrical Potential
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An electric potential can be explained as a location-dependent quantity through which the amount of potential energy per unit of electrical charges can be explained.
- Electric Potential is the force required to move a unit charge from a reference point to a specific point against an electric field.
- It is represnted as V=PEq
- Another important term related to this idea is Electrical Potential Differences which can be described as the differences between two electrical potentials where the final and the initial location differs from each other depending upon when the work was done and the changes due to potential energy.
- Electrical Potential Differences can be represented as-
ΔV = VB - VA = \(\frac{Work}{Charge}\) = \(\frac{ΔPE}{Charge}\)
Ohm’s Law
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This is one of the most basic and important laws of electric circuits. Ohm’s Law states that the voltage across a conductor directly corresponds to the current flowing through it, provided all physical conditions and the temperature remain constant.
Ohms Law Explained
Ohms law video
It is mathematically represented as-
V = IR
- V = voltage expressed in Volts
- I = current expressed in Amps
- R = resistance expressed in Ohms
- If any of the two quantities are known then the third can be calculated by using the following formula:I = V/R and R= V/I.
- The Ohm Law is credited to Georg Simon Ohm (1784-1854), a German physicist who studied the relationship between voltage, current, and resistance.
Resistance
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This is the measure of the opposition by the material to the current flow in a circuit. It is represented in Ohm (Ω). Every material resists current flow to a certain degree. They are either conductors or insulators.
Factors or Laws of Resistance
The resistance of a material depends on four laws. They are:
1. Length of the Substance: The conductive material is directly proportional to the length of the material. It corresponds directly to the length of the material. The resistance of the material increases with the rise in the length of the material and decreases with the decrease in the length of the material.
2. The Cross-Sectional Area of the Substance: The conducting material is inversely proportional to the cross-sectional area of the material. Here the material increases with the decrease in the cross-sectional area of the conductor and decreases with an increase in the cross-sectional area.
3. The Nature of the Material of the Substance: The conducting material depends on the nature of the material. The resistance value of the material changes according to the type of material.
4. The Temperature of the Substance: The conducting material depends on its temperature. The resistance of the material directly corresponds to the temperature.
Here Are Some Important Terms Related To Electric ChargesJoule’s Law Joule’s Law states the rate at which resistance in a circuit is converted from electric energy into heat energy. Discovered by James Prescott Joule in 1840, this law states that the amount of heat per second that develops in a wire carrying a current directly corresponds to the electrical resistance of the wire and the square of the current. Electric Bulb The electric bulb or light bulb is a lighting device that has been used for centuries. It has a transparent light housing with two wires in the center and a thick wire connecting them. The thin wire in between them is the filament. Electric Fuse Electric fuse is a safety device used to protect against an overcurrent. It is a short wire made up of materials that have a low melting point and high resistivity. It is usually made up of metals like zinc, copper, lead, or tin. When a high current passes through it, it melts because of its low melting point. Once the fuse melts it breaks to protect the human body. |
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Things To Remember
- Electricity can be defined a phenomenon that can be associated with stationary or moving electric charges from one matter to the other.
- The S.I. unit of electricity is Watt.
- It is a basic property of every matter.
- The charge is a scalar quantity because it is only a magnitude and has no direction.
- Ohm’s Law states that the voltage across a conductor directly corresponds to the current flowing through it, provided all physical conditions and the temperature remain constant.
Important PYQs Related To Electricity
- A current through a wire depends on time as… (BITSAT 2021)
- Find current, i… (KEAM 2018)
- The current (in ampere) drawn from a… (DUET 2009)
- A galvanometer has a resistance of… (DUET 2006)
- The current I in the circuit shown is… (MHT CET 2015)
- The potential difference that must be applied to stop the fastest… (NEET 2010)
- The potential difference (VA−VB)between the points… (NEET 2016)
- The potential differences across the resistance… (NEET 2016)
- A and B are two conductors carrying a current I in the same… (KCET 2002)
- The current passing through the ideal ammeter in the circuit… (KCET 2007)
- The potential difference between… (KCET 2008)
- The amount of charge flowing per second per unit area… (KEAM)
- Find the current in the 8W resistance in given circuit…
- The potential difference between points…
- Some electric bulbs are connected in series across a...(JKCET 2004)
- The mobility of free electrons… (JKCET 2010)
- The number density of free electrons in a copper conductor… (AMUEEE 2011)
- The potential difference applied to an X-ray tube… (JEE Advanced 2002)
- The mobility of charge carriers increases with...(DUET 2011)
- Identify the INCORRECT statement regarding a superconducting wire...
Sample Questions
Ques: What are the factors that affect resistance?(5 marks)
Ans: The resistance of a material depends on four laws. They are:
- Length of the substance
- The cross-sectional area of substance
- The nature of the material of the substance
- The temperature of the substance
Length of the substance: The conductive material is directly proportional to the length of the material. The resistance of the material is directly proportional to the length of the material. It increases with the increase in the length of the material and decreases with the decrease in the length of the material.
The cross-sectional area of the substance: The conducting material is inversely proportional to the cross-sectional area of the material. Here the material increases with the decrease in the cross-sectional area of the conductor and decreases with an increase in the cross-sectional area.
The nature of the material of the substance: the conducting material depends on the nature of the material. The resistance value of the material changes according to the type of material.
The temperature of the substance: The conducting material depends on its temperature. The resistance of the material directly corresponds to the temperature.
Ques: State Ohm's Law?(2 marks)
Ans: Ohm’s Law states the relationship between current, voltage, and resistance. According to Ohm’s Law, the current flowing through the conductor directly corresponds to the difference applied across the ends of the conductor provided all physical conditions remain the same. It is mathematically represented as
V=IR
V = voltage expressed in Volts
I = current expressed in Amps
R = resistance expressed in Ohms
Ques: State examples for conductors and insulators.(1 mark)
Ans: Some examples of conductors are silver, gold, aluminum, copper, mercury, etc. Some good insulators are rubber, glass, oil, air, and diamond, etc.
Ques: What is an electric circuit?(1 mark)
Ans: The closed path of an electric current is called an electric circuit. It consists of electric devices, wires, and a source of electricity.
Ques: What is Ampere?(1 mark)
Ans: The unit of an electric current is ampere. It is defined as a flow of a single coulomb of charges per second.
Ques: What is the light bulb?(1 mark)
Ans: The electric bulb or light bulb is a lighting device that has been used for centuries. It has a transparent light housing with two wires in the center and a thick wire connecting them. The thin wire in between them is the filament.
Ques: A bulb has 40W, 220 V. What will be the amount of current drawn by it if it is connected to a 220V supply. Find it resistance as well. ( 3 Marks)
Ans: It is mentioned that the power of the bulb is- 40 W
The voltage is- 220W.
Therefore, the amount of current drawn by it will be- I = \(\frac{P}{V}\)= \(\frac{40}{220}\)= \(\frac{2}{11}\)A
where the resistance of the bulb will be- R = \(\frac{V}{I}\)= \(\frac{220}{\frac{2}{11}}\)= \(\frac{220 * 11}{2}\)= 1210Ω
Ques: A current of 10 A flows through a conductor for two minutes. (4 Marks)
(i) Calculate the amount of charge passed through any area of cross section of the conductor.
(ii) If the charge of an electron is 1.6 × 10-19 C, then calculate the total number of electrons flowing.
Ans: It is mentiioned that, I = 10A, t = 2min = 2 x 60sec. =120sec.
(i) the amount of charge passed through any area of cross section of the conductor can be calculated as- I = \(\frac{Q}{t}\)
to simplify this equation as per the informations given in the questions- Q = I x t , therefore, Q = (10 x 120) A s = 1200C
(ii) We also know that Q = ne, here n is the representation of the total number of electrons,
Therefore, 1200 = n x 1.6 x 10-19
or, n = \(\frac{1200}{1.6 * 10{^{21}}}\)= 7.5 x 1021
Ques: Describe a tool that you can use to keep a potential difference between two conductor ends. Describe the procedure this device uses to accomplish the process. (2 Marks)
Ans: To maintain a potential difference between two conductor ends, we can use a cell or battery. Even when no current is pulled from a cell, the chemical process inside of that cell or battery creates the potential difference across its terminals. It generates electricity when linked to a conductor and maintains the potential difference between the ends of the conductor.
Ques: Define the term 'volt'. (1 Mark)
Ans: The S.I. unit for the potential difference is "volt."
When 1 joule of labor is needed to move 1 coulomb of charge from one location to the other, the potential difference between the two points can be measured as 1 volts.
Ques: What is Electrical Potential Differences with its representation. (2 Marks)
Ans: Electrical Potential Differences which can be described as the differences between two electrical potentials where the final and the initial location differs from each other depending upon when the work was done and the changes due to potential energy.
It can be represented as- ΔV = VB - VA = \(\frac{Work}{Charge}\)= \(\frac{ΔPE}{Charge}\)
Ques: What is heating effect? Mention some examples of applications of human effects. (2 Marks)
Ans: As the current passes through the stream, it heats up and produces heat. This is because electrical energy is converted to thermal energy. This is called the heating effect of electric current.
Electrical laundry iron, toaster, heater, electrical bulb and fuses can be considered as a few examples of the heating effect of electric current.
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