Electricity Class 10th CBSE Easy Notes
Electricity is a fundamental form of energy that powers our daily lives. At its core, it involves the movement of electrons, which are tiny particles found within atoms. This movement creates an electric charge, which can be harnessed to perform a wide variety of tasks. Naturally, electricity can be observed during lightning storms, where immense amounts of electric charge are transferred between clouds and the ground.
Electricity Class 10th CBSE Easy Notes
What is Electricity?
Electricity is a form of energy resulting from the existence of charged particles such as electrons or protons. It can be static or dynamic (current electricity).
How and Why Electricity Occurs
Electricity occurs due to the movement of electrons. When these electrons move through a conductor, they create an electric current.
Charge
Charge is a property of matter that causes it to experience a force when placed in an electric and magnetic field.
- S.I. Unit of Charge: Coulomb (C)
- Formula: Q = ne^{-}
- Where Q= charge,
- e^{-} = Charge on 1 electron = -1.6 x 10^{-19} coulombs.
- n = Number of electrons
How Charge Occurs
Charge occurs due to the transfer of electrons between materials, often through friction, conduction, or induction.
Properties of Charge:
- Charges are of two types: positive and negative.
- Like charges repel, unlike charges attract.
- Charge is conserved.
- Charge is quantized.
- Charge on 1 Electron: -1.6 x 10^{-19} coulombs.
- Number of Electrons in 1 Coulomb: 6.25 × 10^{18} electrons
Conductors and Insulators
- Why Metals are Conductors: Metals have free electrons that can move easily.
- Why Non-metals are Insulators: Non-metals do not have free electrons.
- Why Pure Water Does Not Conduct Electricity: Pure water lacks ions. Adding impurities like salts makes it conductive.
Types of Electricity
Static Electricity and Current Electricity
Definition:
- Static Electricity: Static electricity refers to the accumulation of electric charge on the surface of objects. This charge remains in a static (non-moving) state until it is discharged.
- Current Electricity: Current electricity is the flow of electric charge (electrons) through a conductor, such as a wire, in a continuous and steady manner.
Examples:
- Static Electricity Example: When you rub a balloon on your hair, the balloon picks up electrons and becomes negatively charged. If you then bring the balloon close to small pieces of paper, the paper pieces will stick to the balloon due to the static charge.
- Current Electricity Example: When you switch on a flashlight, the electric current flows from the batteries through the bulb, causing it to light up.
Difference Between Static Electricity and Current Electricity:
Aspect | Static Electricity | Current Electricity |
---|---|---|
Definition | Accumulation of electric charges on a surface | Flow of electric charges through a conductor |
Charge Movement | Charges remain stationary | Charges move continuously in a circuit |
Source | Friction, induction, conduction | Batteries, generators, power supplies |
Presence of Circuit | No complete circuit needed | Requires a complete circuit for the flow of charges |
Examples | Rubbing a balloon on hair, lightning | Flashlight, electric appliances, household wiring |
Measurement | Typically measured in coulombs (charge) | Measured in amperes (current) |
Nature of Charge | Typically involves static positive or negative charges | Involves the continuous flow of electrons (current) |
Duration | Charges can stay for a long time until discharged | Current flows as long as the circuit is complete and power is supplied |
Effects | Causes objects to attract or repel each other | Powers electrical devices and causes magnetic effects |
Practical Use | Limited practical applications (e.g., electrostatic painting) | Extensive practical applications in daily life and industry |
Electric Current
Definition: Electric current is the rate of flow of electric charge through a conductor.
- Meaning: Rate of flow of electric charge.
- How it Occurs: When electrons move through a conductor.
- When we say there is 'current in wire': It means electrons are flowing through the wire.
- Formula: I = Q/t
- Meaning of 1 Ampere: 1 Coulomb of charge passing through a point in 1 second.
- 1A = 1cs^{-1}
- Ammeters: Device use to Measure current, connected in series, have very low resistance to minimize circuit interference.
How Electric Current Occurs
Electric current occurs when there is a potential difference across a conductor, causing electrons to flow from the negative side to the positive side.
Electric Potential and Potential Difference
- Electric Potential (Voltage): The work done or energy consumed to move a unit charge from a reference point to a specific point in electric field.
- Formula : V = W/Q
- Potential Difference: Difference in electric potential between two points.
- Formula: V = V_{2} - V_{1}
- S.I. Unit: Volt (V)
- Meaning of 1 Volt: 1 Joule of work is done to move 1 Coulomb of charge.
- 1 volt = 1 Joule / Coulomb ( V = W/Q )
- 1V = 1j/c = 1jc^{-1}
- Voltmeters: It is Device to Measure voltage, connected in parallel, have high resistance to avoid drawing current.
- Electric Potential vs. Potential Difference: Electric potential is the potential energy per charge at a point, whereas potential difference is the difference in potential between two points.
Ohm’s Law
Definition:Ohm's Law states that At constant temperature the current through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance.
At constant temperature,
- V ∝ I
- V= RI ( Where R is proportional constant called Resistance )
- R = V/I
- Resistance = Voltage/ Current
Electric Resistance
Definition: Electric resistance is the opposition that a material offers to the flow of electric current. It is a measure of how much a material resists the movement of electrons.
Resistance Key Points:
- Symbol:R
- S.I. Unit: Ohm (Ω)
- Formula: R=V/I
- 1Ω = 1V / 1A = 1VA^{-1}
$$ $$ - Properties: Depends on material, length, cross-sectional area, and temperature.
- Meaning of 1 Ohm: 1 Volt of potential difference causes 1 Ampere of current.
How resistance occurs?
- When an electric current passes through a material, the electrons collide with the atoms of the material.
- These collisions slow down the flow of electrons, causing resistance.
Examples:
- High Resistance Materials: Rubber, glass, wood
- Low Resistance Materials: Copper, aluminum, silver
Application of Resistance:
- Light Bulb Filament: Made of tungsten, has high resistance, so it heats up and emits light.
- Electrical Wires: Made of copper, has low resistance, so they allow easy flow of current with minimal energy loss.
Concepts related questions/queries:
Q.1: Why Electric Resistance Occurs?
Ans: Resistance occurs due to collisions between the flowing electrons and the atoms of the conductor.
Q.2:What is a Resistor?
A resistor is a component that limits or regulates the flow of electrical current in a circuit.
Q.3:Why We Need Resistors?
Resistors are used to control current, divide voltage, and protect components from damage due to excessive current.
Q.4:How Resistors Work?
Resistors work by converting electrical energy into heat, which dissipates the energy and limits current flow.
Q.5:What is Rheostate (Variable resistance)?
Rheostat (Variable resistance ) is a component used to regulate current without changing the source of voltage.
Types of Combinations of Resistors:
1. Series Combination 2.Parallel Combination
- Series Combination: Resistors are connected end-to-end.
- Formula: ${\mathit{R}}_{\mathit{t}\mathit{o}\mathit{t}\mathit{a}\mathit{l}}={\mathit{R}}_{1}+{\mathit{R}}_{2}+\mathrm{.}\mathrm{.}\mathrm{.}+{\mathit{R}}_{\mathrm{\mathit{n}}}$
Proof:
- Properties: The current is the same through all resistors; the total resistance is the sum of individual resistances.
- Formula: ${\mathit{R}}_{\mathit{t}\mathit{o}\mathit{t}\mathit{a}\mathit{l}}={\mathit{R}}_{1}+{\mathit{R}}_{2}+\mathrm{.}\mathrm{.}\mathrm{.}+{\mathit{R}}_{\mathrm{\mathit{n}}}$
- Parallel Combination: Resistors are connected across the same two points.
- Formula: $\frac{1}{{\mathit{R}}_{\mathit{t}\mathit{o}\mathit{t}\mathit{a}\mathit{l}}}=\frac{1}{{\mathit{R}}_{1}}+\frac{1}{{\mathit{R}}_{2}}+\mathrm{.}\mathrm{.}\mathrm{.}+\frac{1}{{\mathit{R}}_{\mathrm{\mathit{n}}}}$
Proof:
- Properties: The voltage is the same across all resistors; the total resistance is less than the smallest individual resistance.
- Formula: $\frac{1}{{\mathit{R}}_{\mathit{t}\mathit{o}\mathit{t}\mathit{a}\mathit{l}}}=\frac{1}{{\mathit{R}}_{1}}+\frac{1}{{\mathit{R}}_{2}}+\mathrm{.}\mathrm{.}\mathrm{.}+\frac{1}{{\mathit{R}}_{\mathrm{\mathit{n}}}}$
Advantages and Disadvantages of Combinations
Combination | Advantages | Disadvantages |
---|---|---|
Series | Simple to design | If one fails, the entire circuit fails |
Parallel | If one fails, others still work | More complex to design |
Factors Affecting Resistance
Factors Affecting Resistance
- Length: Resistance is directly proportional to the length of the conductor.
- Area: Resistance is inversely proportional to the cross-sectional area.
- Material: Different materials have different intrinsic resistivities.
Mathematically:
- Length (L): R ∝ L ...(i)
- $\mathrm{Area(A):R\; \propto \frac{\mathrm{1/A\; ...(ii)}}{}}$
$\mathrm{From\; (i)\; and\; (ii)\; :\; R\; \propto \; L/A}$
- R = ρL/A , Where ρ (rho) is proportional constant called Resistivity.
- ρ = RA/L
Resistivity (ρ):
What is Resistivity?
Ans: Resistivity is a material-specific property that quantifies how strongly a material opposes the flow of electric current.
Why Resistivity Occurs in material?
Resistivity arises due to the intrinsic properties/ Inherent property of the material.
- Formula: ρ = RA/L
- S.I unit : ohm-meter
- 1 Ohm-meter: One ohm meter (Ω·m) is the unit of electrical resistivity, representing the resistance of a material with a one-meter length and a one-square-meter cross-sectional area.
Resistance vs. Resistivity
- Resistance: Depends on the shape and size of the material.
- Resistivity: Inherent property of the material, independent of shape and size.
Property | Resistance (R) | Resistivity (ρ) |
---|---|---|
Definition | Opposition to current flow | Inherent property of material |
Unit | Ohm (Ω) | Ohm-meter (Ω·m) |
Dependence | Length, area, temperature | Material only |
Formula | 𝑅 = V/I | ρ=𝑅A/L $\frac{}{}$ |
Numericals Related to Ohm’s Law, Resistance, and Resistivity
- Ohm's Law: Calculate current when voltage is 10V and resistance is 5Ω. $\mathit{I}=\frac{\mathit{V}}{\mathit{R}}=\frac{10}{5}=2\mathit{A}$
- Resistance: Find resistance when length is 2m, area is 1m², and resistivity is 1.68 x 10^{-8} Ω·m. $\mathit{R}=\mathit{\rho}\frac{\mathit{L}}{\mathit{A}}=1.68\times 1{0}^{-8}\frac{2}{1}=3.36\times 1{0}^{-8}\mathrm{\Omega}$
- Resistivity: Calculate resistivity when resistance is 10Ω, length is 5m, and area is 0.01m². $\mathit{\rho}=\mathit{R}\frac{\mathit{A}}{\mathit{L}}=10\frac{0.01}{5}=0.02\mathrm{\Omega}\cdot \mathit{m}$
- Current Formula: Calculate charge flow when current is 2A for 5 seconds. $\mathit{Q}=\mathit{I}\mathit{t}=2\times 5=10\mathit{C}$
- Charge on Electron: Find the number of electrons in 10C of charge. $\mathit{n}=\frac{\mathit{Q}}{\mathit{e}}=\frac{10}{1.6\times 1{0}^{-19}}=6.25\times 1{0}^{19}$
Numericals with Solutions Related to Series and Parallel Combinations
- Series: Calculate total resistance for 3Ω, 5Ω, and 2Ω resistors. ${\mathit{R}}_{\mathit{t}\mathit{o}\mathit{t}\mathit{a}\mathit{l}}=3+5+2=10\mathrm{\Omega}$
- Parallel: Calculate total resistance for 6Ω and 3Ω resistors. $\frac{1}{{\mathit{R}}_{\mathit{t}\mathit{o}\mathit{t}\mathit{a}\mathit{l}}}=\frac{1}{6}+\frac{1}{3}=\frac{1}{2}\to {\mathit{R}}_{\mathit{t}\mathit{o}\mathit{t}\mathit{a}\mathit{l}}=2\mathrm{\Omega}$
- Mixed: Calculate total resistance for 2Ω and 4Ω in series, in parallel with 3Ω. ${\mathit{R}}_{\mathit{s}\mathit{e}\mathit{r}\mathit{i}\mathit{e}\mathit{s}}=2+4=6\mathrm{\Omega}$
$\frac{1}{{\mathit{R}}_{\mathit{t}\mathit{o}\mathit{t}\mathit{a}\mathit{l}}}=\frac{1}{6}+\frac{1}{3}=\frac{1}{2}\to {\mathit{R}}_{\mathit{t}\mathit{o}\mathit{t}\mathit{a}\mathit{l}}=2\mathrm{\Omega}$
- Series Current: Find current for 10V source and 10Ω total resistance. $\mathit{I}=\frac{\mathit{V}}{\mathit{R}}=\frac{10}{10}=1\mathit{A}$
- Parallel Voltage: Calculate voltage across 2Ω and 4Ω in series, in parallel with 3Ω, for 6V source. ${\mathit{R}}_{\mathit{s}\mathit{e}\mathit{r}\mathit{i}\mathit{e}\mathit{s}}=2+4=6\mathrm{\Omega}$
$\frac{1}{{\mathit{R}}_{\mathit{t}\mathit{o}\mathit{t}\mathit{a}\mathit{l}}}=\frac{1}{6}+\frac{1}{3}=\frac{1}{2}\to {\mathit{R}}_{\mathit{t}\mathit{o}\mathit{t}\mathit{a}\mathit{l}}=2\mathrm{\Omega}$
$\mathit{V}=\mathit{I}\mathit{R}=1\times 2=2\mathit{V}$
Electric Power
Electric power is the rate at which electrical energy is transferred by an electric circuit.
- Formula : Power = work/Time = Energy/ Time
- S.I. Unit: Watt (W)
- 1watt = 1j/s = 1js^{-1}
- Commercial Unit: Kilowatt-hour (kWh) = Unit
- Meaning of 1 Watt: 1 Joule of energy per second.
- Proof of formulas:
Electric Energy:
Electric energy is the energy transferred by an electric circuit.
- Formula: E=P×t
- S.I. Unit: Joule (J)
- Meaning of 1 Joule: Energy used when 1 Ampere flows for 1 second under 1 Volt.
- Commercial Unit: 1 kWh (or 1 unit)
- 1 kWh: 1 kilowatt of power used for 1 hour.
Proof of Formulas of Electric Energy
Joule’s Law of Heating
Joule's Law states that the heat produced in a conductor is proportional to the square of the current, the resistance, and the time.
$\mathit{H}={\mathit{I}}^{2}\mathit{R}$
Heating Mechanism for Appliances
- Iron Press: Electrical energy is converted into heat using a resistive element.
- Heater: Similar to iron, but designed for room heating, with larger resistive elements.
Relation Between S.I. Unit and Commercial Unit of Electric Energy
Arrangement of Domestic Wiring in India
Domestic wiring in India uses parallel combinations to ensure that if one appliance fails, others continue to work.
Advantages and Disadvantages of Combinations
Combination | Advantages | Disadvantages |
---|---|---|
Series | Simple to design | If one fails, the entire circuit fails |
Parallel | If one fails, others still work | More complex to design |
Why Parallel Combination in Domestic Wiring?
Ans: Parallel combinations provide uniform voltage across all appliances and allow independent operation.
Electric Fuse
Electric Fuse- An electric fuse is a safety device that protects electrical circuits from damage caused by excess current. It is made of a thin wire that melts when the current exceeds a certain level, breaking the circuit.
Electric Fuse Importance
- Protection: It protects electrical appliances and wiring from damage due to overload or short circuits.
- Safety: It prevents potential fires and electric shocks by interrupting excessive current flow.
- Cost-Effective: Fuses are a simple and inexpensive way to protect electrical systems.
How Does an Electric Fuse Work?
Ans:Fuses contain a wire that melts when excessive current flows through it, breaking the circuit and preventing damage.
- Circuit Integration: The fuse is placed in series with the electrical circuit.
- Current Flow: Under normal conditions, the current flows through the fuse wire without any issues.
- Overload/Short Circuit: When the current exceeds the fuse's rating, the fuse wire heats up and melts.
- Circuit Break: Melting of the fuse wire breaks the circuit, stopping the flow of electricity and protecting the system.
Types of Electric Fuses
Types of Electric Fuses
- Cartridge Fuse: Enclosed in a cylindrical body with metal end caps.
- Plug Fuse: Fits into a socket and is commonly used in household applications.
- Blade Fuse: Flat and used in automobiles.
- Drop-Out Fuse: Used in high-voltage applications, usually mounted on poles.
- Resettable Fuse: Can be reset after tripping instead of being replaced.
Fuse strength measurements Unit:
- The capacity of a fuse is measured in amperes (A). This indicates the maximum current that the fuse can handle before it blows.
Deciding Fuse Rating
The fuse rating should be slightly higher than the maximum current expected in the circuit.
- Choose a fuse with a current rating slightly higher than the normal operating current to avoid nuisance blowing but not too high to ensure protection. Typically, a margin of 25-50% is used.
Example Calculation:
- Appliance Power Rating: 1200W
- Operating Voltage: 240V
- Calculate Operating Current:
Sol. Given, P = 1200W
V= 240V
$I=\frac{P}{V}=\frac{1200\mathit{W}}{240\mathit{V}}$
I = 5A
Safety Margin: Add 25%:
$\mathrm{5A}\times 1.25=6.25\mathit{A}$
Hence, Choose the next standard fuse rating, typically 7A for a safe margin.
Practical Example:
- Identify the Operating Current:
- A toaster operates at 1500W with a 230V supply.
- $I=\frac{\mathit{P}}{\mathit{V}}=\frac{1500\mathit{W}}{230\mathit{V}}\approx 6.52\mathit{A}$
$\mathrm{Choose\; the\; Fuse\; Rating:Apply\; a\; safety\; margin:6.52\mathit{A}\times 1.25\approx 8.15\mathit{A}}$
Hence, Choose an 8A or 10A fuse based on standard available ratings.
Numerical Problems on Electric Fuse
- Problem 1:A fuse wire is rated at 5A. If the household circuit operates at 230V, what is the maximum power that can be safely used in the circuit?
- Solution: P = V × I = 230V × 5A = 1150W.
- Problem 2:If an electric iron uses a 10A fuse and operates at 220V, calculate the power consumed by the iron.
- Solution: P = V × I = 220V × 10A = 2200W.
- Problem 3:An electric heater draws a current of 8A. If the power rating of the heater is 1760W, determine the operating voltage.
- Solution: V = P / I = 1760W / 8A = 220V.
- Problem 4:A television set uses a fuse of 2A rating. If the voltage supply is 240V, calculate the maximum power the television set can use without blowing the fuse.
- Solution: P = V × I = 240V × 2A = 480W.
- Problem 5:A refrigerator runs on 5A current and the voltage supply is 230V. If a fuse of 10A is used, explain whether the fuse is appropriately rated or not.
- Solution: The power used by the refrigerator is P = V × I = 230V × 5A = 1150W. The fuse of 10A allows up to 230V × 10A = 2300W. The fuse is appropriately rated as it is higher than the refrigerator's requirement.
Earthing
What is Earthing?
Earthing, also called grounding, is the process of transferring the immediate discharge of electrical energy directly to the Earth with the help of a low-resistance wire.
Why is Earthing important?
- Safety: It protects people from electric shocks.
- Device Protection: It prevents damage to electrical appliances by diverting excess electricity.
- Fire Prevention: It reduces the risk of electrical fires by preventing current build-up.
How does Earthing work?
- Connection to Earth: A conductive wire (usually copper) connects the electrical system to the ground.
- Earth Electrode: The wire is connected to an earth electrode buried in the ground, which provides a path for excess electricity to flow.
- Current Flow: When there's a fault, excess current travels through the earthing wire to the earth, preventing it from causing harm.
Components of Earthing System
- Earthing Rod/Electrode: A metal rod inserted into the ground.
- Earthing Wire: Conductive wire connecting the electrical system to the earthing rod.
- Ground Plate (optional): A metal plate buried in the earth for better contact.
Types of Earthing
- Plate Earthing: Uses a metal plate buried in the ground.
- Rod Earthing: Uses a metal rod driven into the earth.
- Strip or Wire Earthing: Uses a metal strip or wire buried in a trench.
Numericals:
Q.1 Calculate the total resistance of three resistors, 2Ω, 4Ω, and 6Ω, connected in series.
Solution: R_{total} = 2Ω + 4Ω + 6Ω = 12Ω
Q.2 Calculate the total resistance of three resistors, 2Ω, 4Ω, and 6Ω, connected in parallel.
Solution: 1/R_{total} = 1/2 + 1/4 + 1/6 = 0.5 + 0.25 + 0.1667 = 0.9167; R_{total} ≈ 1.09Ω
Q.3 Find the current through a 5Ω resistor if connected in series with a 10Ω resistor and a voltage supply of 15V.
Solution: I = V / R_{total} = 15V / (5Ω + 10Ω) = 15V / 15Ω = 1A
Q.4 In a parallel circuit, two resistors, 3Ω, and 6Ω, are connected to a 12V battery. Calculate the current through each resistor.
Solution: I_{1} = V / R_{1} = 12V / 3Ω = 4A; I_{2} = V / R_{2} = 12V / 6Ω = 2A
Q. Determine the equivalent resistance of a 3Ω resistor in series with a combination of two parallel resistors of 4Ω and 12Ω.
Solution: 1/R_{parallel} = 1/4 + 1/12 = 0.333; R_{parallel} = 3Ω; R_{total} = 3Ω + 3Ω = 6Ω
Frequently Asked Questions (FAQs)
What is electric current?
- Answer: Electric current is the amount of charge flowing through a particular area in unit time. It is measured in amperes (A). One ampere is constituted by the flow of one coulomb of charge per second.
How can you calculate the amount of charge passed through a conductor?
- Answer: The amount of charge (Q) passed through any area of cross-section of a conductor can be calculated using the formula (Q = I × t), where (I) is the current in amperes and (t) is the time in seconds.
What is Ohm’s Law?
- Answer: Ohm’s Law states that the potential difference (V) across the ends of a given metallic wire in an electric circuit is directly proportional to the current flowing through it, provided its temperature remains the same. Mathematically, (V = IR), where (R) is the resistance of the conductor.
How can you maintain a potential difference between the ends of a conductor?
- Answer: A cell or a battery can be used to maintain a potential difference between the ends of a conductor. The chemical reaction within a cell generates the potential difference across its terminals, even when no current is drawn from it. When connected to a conductor, it produces electric current and maintains the potential difference across the ends of the conductor.
How can you find the resistance of a material from a V-I graph?
- Answer: The inverse of the slope of the I-V graph gives the resistance of the material. If the slope of the graph is highest, then the corresponding material has the highest resistance
What is the difference between a series and a parallel circuit?
- Ans: In a series circuit, components are connected end-to-end, resulting in a single path for current flow. In a parallel circuit, components are connected across common points, providing multiple paths for current.
Why are ammeters connected in series and voltmeters in parallel?
- Ans: Ammeters are connected in series to measure the current flowing through the circuit without altering it. Voltmeters are connected in parallel to measure the potential difference across components without drawing significant current.
What is the significance of the kilowatt-hour (kWh) unit?
- Ans:The kilowatt-hour is a commercial unit of electrical energy, widely used for billing purposes. It represents the energy consumption of one kilowatt of power used for one hour.
How does anelectric fuse protect a circuit?
- Ans: An electric fuse protects a circuit by breaking the connection when the current exceeds a safe level. The fuse wire melts, interrupting the flow of electricity and preventing damage to the circuit.
What are the advantages of parallel circuits in domestic wiring?
- Parallel circuits in domestic wiring ensure that each appliance operates independently with consistent voltage, enhancing reliability and safety.
What is Electric Current?
- A: Electric current is the flow of electric charge through a conductor. It is measured in amperes (A) using an ammeter. The direction of conventional current is from the positive terminal to the negative terminal of a battery.
What is the formula for calculating electric current?
- A: Electric current (I) can be calculated using the formula:𝐼=𝑄/t
What is Ohm’s Law?
- A: Ohm’s Law states that the current through a conductor between two points is directly proportional to the voltage across the two points, provided the temperature remains constant. It is expressed as:
What is electrical resistance and its unit?
- A: Electrical resistance is a measure of the opposition to the flow of current in a conductor. It is measured in ohms (Ω). The resistance can be calculated using the formula:𝑅= 𝑉/𝐼
What factors affect the resistance of a conductor?
- A: The resistance of a conductor depends on:Length of the conductor (R is directly proportional to length)Cross-sectional area (R is inversely proportional to area)Material of the conductor (different materials have different resistivities)Temperature (resistance increases with an increase in temperature for most conductors)
What is the difference between series and parallel circuits?
Aspect Series Circuit Parallel Circuit Definition A circuit where components are connected end-to-end, so the current flows through each component one after another. A circuit where components are connected across common points, providing multiple paths for the current. Current The same current flows through all components. The current is divided among the parallel branches, with each branch receiving a fraction of the total current. Voltage The total voltage is the sum of the voltages across each component. The voltage across each component is the same and equal to the total supply voltage. Resistance The total resistance is the sum of the resistances of each component. The total resistance is less than the smallest individual resistance of any branch. Failure of One Component If one component fails, the entire circuit is broken, and current stops flowing. If one component fails, the other branches continue to operate, as current can still flow through the remaining branches. Brightness of Bulbs If identical bulbs are used, their brightness decreases as more bulbs are added. If identical bulbs are used, their brightness remains the same regardless of the number of bulbs. Applications Used in devices where a consistent current is needed through all components, such as Christmas tree lights. Used in household wiring and other applications where consistent voltage across components is required, such as in parallel lighting circuits. Calculation of Total Resistance ${\mathit{R}}_{\mathit{t}\mathit{o}\mathit{t}\mathit{a}\mathit{l}}={\mathit{R}}_{1}+{\mathit{R}}_{2}+{\mathit{R}}_{3}+\cdots $
$\frac{1}{{\mathit{R}}_{\mathit{t}\mathit{o}\mathit{t}\mathit{a}\mathit{l}}}=\frac{1}{{\mathit{R}}_{1}}+\frac{1}{{\mathit{R}}_{2}}+\frac{1}{{\mathit{R}}_{3}}+\cdots $
Example A series circuit with a battery, a switch, and two light bulbs connected in a single path. A parallel circuit with a battery, a switch, and two light bulbs connected across two different paths.
- What is electric power and how is it calculated?
- A: Electric power is the rate at which electrical energy is consumed or converted into other forms of energy. It is measured in watts (W).
- The formula for power is: P=VI
- 𝑃=𝐼^{2}𝑅
What is the unit of electrical energy consumption?
- A: The unit of electrical energy consumption is the kilowatt-hour (kWh), which is also known as a unit. One kilowatt-hour is the amount of energy consumed by a 1 kW device running for 1 hour.
What is a fuse and how does it work?
- A: A fuse is a safety device that protects electrical circuits by breaking the circuit when excessive current flows through it. It contains a thin wire that melts when the current exceeds a certain limit, thus interrupting the flow of electricity and preventing damage to the circuit.
Why are copper and aluminum used for electrical transmission lines?
- A: Copper and aluminum are used for electrical transmission lines because they have low resistivity, which means they conduct electricity efficiently. Copper has higher conductivity, but aluminum is lighter and less expensive, making it suitable for long-distance transmission lines.
Important links
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