Electricity Fundamentals - Grade 10

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Questions and Answers

What are the two types of charge?

  • Light and Dark
  • Small and Large
  • Hot and Cold
  • Negative and Positive (correct)

What is the SI unit of charge?

Coulomb

What is the smallest independent charge?

Electron

What is the formula for calculating the potential difference between two points?

<p>V = W/Q</p> Signup and view all the answers

What is the instrument used to measure the potential difference?

<p>Voltmeter</p> Signup and view all the answers

What is the instrument used to measure the current?

<p>Ammeter</p> Signup and view all the answers

What is the direction of the conventional current?

<p>Opposite to the direction of electron flow</p> Signup and view all the answers

What is the definition of resistance?

<p>Obstruction offered to the flow of charges (current)</p> Signup and view all the answers

What is the formula for calculating resistance?

<p>R = P * L / A</p> Signup and view all the answers

What is the unit of resistivity?

<p>Ohm-meter</p> Signup and view all the answers

Metals generally have high resistivity.

<p>False (B)</p> Signup and view all the answers

Insulators have low resistivity.

<p>False (B)</p> Signup and view all the answers

What is Ohm's Law?

<p>The potential difference (V) across the ends of a metallic conductor is directly proportional to the current (I) flowing through it provided its temperature remains the same.</p> Signup and view all the answers

What is the mathematical expression of Ohm's Law?

<p>V = I * R</p> Signup and view all the answers

What is the unit of power?

<p>watt</p> Signup and view all the answers

What is the formula for calculating power in an electrical circuit?

<p>P = V * I</p> Signup and view all the answers

What is the unit of electrical energy?

<p>Joule</p> Signup and view all the answers

What is the formula for calculating electrical energy?

<p>E = P * t</p> Signup and view all the answers

How can the electrical energy consumed by a device be calculated?

<p>By multiplying the number of units (kWh) by the price of the unit</p> Signup and view all the answers

Match the following terms with their definitions:

<p>Electric current = The flow of electric charge Voltage = The potential difference between two points in a circuit Resistance = The opposition to the flow of electric current Power = The rate at which energy is transferred or used Energy = The ability to do work</p> Signup and view all the answers

A circuit breaker is used to prevent electrical overloads by stopping the flow of current when the current exceeds a safe limit.

<p>True (A)</p> Signup and view all the answers

A fuse wire is a safety device that is used to prevent short circuits by interrupting the flow of current when the current exceeds a safe limit.

<p>True (A)</p> Signup and view all the answers

What is the main principle behind the heating effect of electric current?

<p>Joule's Law of Heating</p> Signup and view all the answers

Which of the following is NOT a practical application of the heating effect of electric current?

<p>Electric Fan (B)</p> Signup and view all the answers

Why is Tungsten used in electric bulbs?

<p>Tungsten has a high melting point and can withstand the high temperatures generated when electricity flows through it.</p> Signup and view all the answers

What is the purpose of an electric fuse?

<p>To prevent short circuits by interrupting the flow of current when the current exceeds a safe limit.</p> Signup and view all the answers

Fuse wire should have low resistivity.

<p>False (B)</p> Signup and view all the answers

A fuse wire should have a low melting point.

<p>True (A)</p> Signup and view all the answers

The rating of a fuse wire refers to the maximum current that can flow through it before it melts

<p>True (A)</p> Signup and view all the answers

What is the S.I unit of current?

<p>Ampere</p> Signup and view all the answers

What is the definition of 1 ampere?

<p>The current flowing through a conductor is known as one ampere if one coulomb of charge flows through it in one second.</p> Signup and view all the answers

What is the S.I unit of potential difference?

<p>Volt</p> Signup and view all the answers

What is the definition of 1 volt?

<p>The potential difference between two points is said to be 1 volt if 1 Joule of work is done in moving a positive charge of 1 Coulomb from one point to the other.</p> Signup and view all the answers

What is the S.I unit of resistance?

<p>Ohm</p> Signup and view all the answers

Flashcards

Charge (Q)

Two types: positive (+) and negative (-). SI unit is Coulomb (C).

Electron

Smallest independent charge, negative charge of 1e = 1.6 x 10⁻¹⁹ C.

Current (I)

Rate of flow of charge; measured in Amperes (A).

Potential Difference (PD)

Work done in moving 1 Coulomb of charge between two points; measured in Volts (V).

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Voltage Formula

V = W/Q, where W is work done and Q is charge.

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Resistance (R)

Obstruction to the flow of current; measured in Ohms (Ω).

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Ohm's Law

V = IR; Voltage is directly proportional to current at constant temperature.

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Resistivity (P)

Property of a material to resist current, measured in Ωm.

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Series Circuit

Same current through all components; total resistance is the sum of individual resistances.

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Parallel Circuit

Same voltage across all components; current can differ.

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Electric Power

Rate of energy consumption; measured in Watts (W). P = VI.

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Electric Energy

Energy supplied by a cell; measured in Joules (J). E = P x t.

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Heating Effect of Current

When current passes through a conductor, it produces heat.

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Joule's Law of Heating

H = i²Rt; heat produced in a resistor is proportional to the square of current.

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Electric Fuse

Safety device that melts to stop current flow during overload.

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Coulomb

SI unit of electric charge.

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Ampere

SI unit of electric current; 1 A = 1 C/s.

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Volt

SI unit of potential difference; 1 V = 1 J/C.

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Ohm

SI unit of resistance; 1 Ω = 1 V/A.

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Kilowatt-hour (kWh)

Unit of energy; 1 kWh = 3.6 x 10⁵ J.

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Resistance Factors

Resistance depends on length, area, material, and temperature.

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Filament in Bulb

Made of tungsten; emits light when heated.

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Ammeter

Device used to measure current in a circuit.

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Voltmeter

Device used to measure potential difference.

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Electric Circuit

Continuous and closed path for electric current.

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Power Formula

P = VI; power can also be calculated as P = i²R or P = V²/R.

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Energy Bill

Cost calculated as number of units consumed × price per unit.

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Study Notes

Electricity

  • Charge (Q):

    • Two types of charge (positive and negative)
    • SI unit of charge: Coulomb (C)
    • Smallest independent charge: electron charge (e = 1.6 × 10-19 C)
    • Opposite charges attract, like charges repel

  • Current (I):

    • Rate of flow of charge
    • Direction of current: opposite to the flow of electrons
    • SI unit of current: Ampere (A)
    • Current = Charge / Time (I = Q/t)

  • Potential Difference (P.D) (V):

    • Amount of work done in moving a unit charge from one point to another
    • SI unit: Volt (V)
    • Potential difference = Work/Charge (V = W/Q)
    • Measured using a voltmeter
    • Electrons flow from lower potential to higher potential

  • Current (I) and Potential Difference (V):

    • Measured by an ammeter
    • Electron flow from higher potential to lower potential

  • Resistance (R):

    • Obstruction to the flow of charges (current)
    • Property of a conductor to obstruct the flow of charges
    • SI unit: Ohm (Ω)

Resistance Factors

  • Resistance depends on:

    • Material (resistivity): property of material (ρ)
    • Length (l)
    • Cross-sectional area (A)
    • Temperature (T)

  • Resistance formula: R = ρl/A

  • Resistivity (ρ):

    • Material property
    • SI unit: Ωm
    • Metals and Alloys have low resistivity (good conductors)
    • Insulators (like rubber, glass) have high resistivity

Ohm's Law

  • Potential difference (V) across a conductor is directly proportional to the current (I) flowing through it, provided the temperature remains constant.
  • Formula: V = IR

Resistor Combinations

  • Series:

    • Current is same in all resistors
    • Total resistance is the sum of individual resistances (RT = R1 + R2 + R3)
    • Potential difference is different across each resistor

  • Parallel:

    • Potential difference is same across all resistors
    • Reciprocal of total resistance is the sum of reciprocals of individual resistances (1/RT = 1/R1 + 1/R2 + 1/R3)
    • Current is different in each resistor

Heating Effect of Electric Current

  • When current passes through a conductor, it generates heat.
  • Joule's Law of Heating: Heat produced (H) = I2Rt
  • Practical applications: electric bulb, heater, toaster

Electric Fuse

  • Safety device to prevent short circuits
  • Contains a wire with a low melting point
  • When high current flows, the wire melts, stopping further current flow
  • Fuse wire is placed in series with the appliance

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