Electricity Basics: Current, Static Electricity, and Matter Structure
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Questions and Answers

What component in a simple electrical circuit is used to control the amount of current?

  • A cell
  • A switch
  • A resistor (correct)
  • An ammeter

    • What is the unit of electric current?

  • Joule
  • Ohm
  • Ampere (correct)
  • Volt

    • Through which component should an ammeter be connected in a circuit?

  • In series with the resistance (correct)
  • Across the source terminals
  • Parallel to the resistance
  • Parallel to the source

    • What is the conventional direction of current flow in a circuit?

    <p>From positive to negative terminal</p> Signup and view all the answers

    How is 1 milli-ampere written in terms of amperes?

    <p>1 x 10-3 A</p> Signup and view all the answers

    Which formula represents the electromotive force (EMF) in a system?

    <p>EMF = VT + IR</p> Signup and view all the answers

    What is measured in volts using a voltmeter in a circuit?

    <p>Potential difference</p> Signup and view all the answers

    How is the voltage available at the terminal of the source of supply denoted?

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

    What is electric current?

    <p>Electricity in motion</p> Signup and view all the answers

    What is a molecule?

    <p>The smallest particle of a substance that has the properties of the substance</p> Signup and view all the answers

    What is the charge of a proton?

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

    Which sub-atomic particle is electrically neutral?

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

    In an atom, where are the electrons located?

    <p>Orbiting around the nucleus</p> Signup and view all the answers

    What is the K shell?

    <p>The innermost shell of electrons around the nucleus</p> Signup and view all the answers

    Which of the following is a common conductor?

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

    Which of these materials is an insulator?

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

    Which element is a common semiconductor?

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

    How many electrons does the 'L' shell in a copper atom hold?

    <p>8</p> Signup and view all the answers

    Study Notes

    Structure of Matter

    • Matter is anything that has mass and occupies space.
    • A matter is made of tiny, invisible particles called molecules.
    • A molecule is the smallest particle of a substance that has the properties of the substance.
    • Each molecule can be divided into simpler parts by chemical means.
    • The simplest parts of a molecule are called atoms.

    Atomic Structure

    • An atom contains three types of sub-atomic particles: electrons, protons, and neutrons.
    • Protons and neutrons are located in the centre or nucleus of the atom.
    • Electrons travel around the nucleus in orbits.
    • Nucleus contains protons and neutrons in equal numbers.
    • Protons have a positive electrical charge and are almost 1840 times heavier than electrons.
    • Electrons have a negative electric charge and are three times larger in diameter than protons.
    • Neutrons are electrically neutral.

    Energy Shells

    • Electrons are arranged in shells around the nucleus.
    • A shell is an orbiting layer or energy level of one or more electrons.
    • Major shell layers are identified by numbers or by letters starting with 'K' nearest the nucleus and continuing alphabetically outwards.
    • There is a maximum number of electrons that can be contained in each shell.
    • Example: a copper atom with 29 electrons would have four shells with a number of electrons in each shell.

    Conductors

    • Conductors are materials that have many valance electrons, permitting electrons to move through them easily.
    • Generally, conductors have one, two, or three electrons in their shells.
    • Most metals are conductors.
    • Examples of good conductors: Copper, Aluminium, Zinc, Lead, Tin, Eureka, Nichrome, etc.
    • Silver and gold are very good conductors.

    Insulators

    • Insulators are materials that have few, if any, free electrons and resist the flow of electrons.
    • Generally, insulators have five, six, or seven electrons in their shells.
    • Examples of insulators: air, glass, rubber, plastic, paper, porcelain, PVC, fibre, mica, etc.

    Semiconductors

    • Semiconductors are materials that have some of the characteristics of both conductors and insulators.
    • Semiconductors have valence shells containing four electrons.
    • Examples of pure semiconductor materials: silicon and germanium.

    Simple Electrical Circuit

    • A simple electrical circuit consists of:
      • An energy source (cell) to provide voltage needed to force the current through the circuit.
      • Conductors through which the current can flow.
      • A load (resistor 'R') to control the amount of current and to convert electrical energy to other forms.
      • A control device (switch 'S') to start or stop the flow of current.

    Electric Current

    • Electric current is the flow of free electrons in a definite direction.
    • Current is defined as the amount of charge 'Q' transferred over a time 't'.
    • Conventional flow of current is opposite to the direction of the flow of electrons.
    • Unit of current (I) is an ampere (A).
    • Multiples of the ampere: 1 kA = 1000 A, 1 mA = 1/1000 A, 1 μA = 1/1000000 A.

    Electromotive Force (EMF)

    • EMF is the electrical force that causes free electrons to move in a conductor.
    • Unit of EMF is 'Volt' and is denoted by letter 'E'.
    • EMF cannot be measured by any meter, only calculated using the formula E = V + IR.

    Potential Difference (PD)

    • Potential Difference is the difference of voltage and pressure across two points in a circuit.
    • Measured in volts.
    • Calculated using the formula EMF = V1 + IR.

    Terminal Voltage (p.d)

    • Terminal voltage is the voltage available at the terminal of the source of supply.
    • Symbol is VT and unit is also the volt.
    • Calculated using the formula V1 = EMF - IR.

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    Learn about the basics of electricity, including electric current, static electricity, and the structure of matter, including molecules and atoms.

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