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  1. What are tiny particles that matter is made of called?

  • compounds
  • atoms (correct)
  • ions
  • protons and neutrons

    1. What are elements called that have atoms with electrons that are easily freed?

  • ions
  • insulators
  • conductors (correct)
  • elements

    • which of the following contains atoms of more than one type?

  • element
  • 0
  • 0
  • compounds (correct)

    • which method is most used to produce electrical energy?

    <p>magnetism is most used to produce electrical energy</p> Signup and view all the answers

    Energy can be neither created nor destroyed

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

    What letter represents the unit of electric charge?

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

    What is the unit for current?

    <p>I or A</p> Signup and view all the answers

    if eight coulombs of charge pass a given point in a conductor over a period of four seconds, current is flowing at a rate of how many amperes? 8/4=2

    <p>2 amperes</p> Signup and view all the answers

    if 1800 joules of work are required to move 4 coulombs of charge from one point to another, then the potential difference between the two points is how many volts?

    <p>450 volts</p> Signup and view all the answers

    What is resistance ?

    <p>resistance, that opposes the flow of electric current.</p> Signup and view all the answers

    Write out the three equations forms of ohms law

    <ol> <li>I=E/R</li> <li>R=E/I</li> <li>E=I*R</li> </ol> Signup and view all the answers

    if a circuit had a current flow of 8 A and the resistance is 20, what is the pressure in volts?

    <p>8*20=160 volts</p> Signup and view all the answers

    if a circuit has a current flow of 5 A and a pressure of 120 V, what is the resistance ?

    <p>24 R</p> Signup and view all the answers

    how much power will a heater produce if it uses 15 A in a 120 v electrical system ? volts x amps or P= E x I

    <p>1800 W</p> Signup and view all the answers

    how many amps will flow through a 60 W headlight bulb in a 24 V system? p=E x I

    <p>2.5 A</p> Signup and view all the answers

    four main types of electrical drawings: 1. pictorial, 2. block diagrams, 3. wiring diagrams 4. schematic diagram

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

    Which type of diagrams are the easiest to understand for someone with no experience in the electrical trade?

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

    one line diagrams uses symbols for the components and block diagram uses only blocks.

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

    list three distinguishing characteristics of one-line diagrams: 1. to represent a clear picture of the main in line components in the system or circuit. 2. one line diagrams commonly show the highest voltage 3. the components are labelled to show their name, type and sometimes even their catalogue.

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

    six sources of EMF are: friction, chemical, pressure, heat, light and magnetism

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

    one coulomb equal to: 6.24*10(18)= 6, 240, 000, 000, 000, 000, 000

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

    List two hazards of electrostatic charge: lighting and fuel handling

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

    Voltage is the driving force of current, it is the electromotive force which pushes free electrons from one atom to another in the same direction.

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

    electric power is the rate at which work is done or energy is transformed into an electrical circuit.

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

    The current flowing in an electric circuit is directly proportional to the applied voltage an inversely proportional to the resistance of the circuit.

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

    the power in a circuit equals the product of the voltage and the current in the circuit.

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

    Wiring diagram shows as clearly as possible, the actual location of all the components of a circuit

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

    When two wires across, a dot is used to indicate that the wires are connected

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

    If a dot is not shown, the wires across each other but do not connect electrically

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

    The schematic diagram shows electrical relationship between the components of a circuit

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

    The term circuit refers to a circular journey or loop. In the case of an electric circuit, it is the journey or loop travelled by the electrons. Therefore, three basic conditions must exist to have a complete circuit so that electron may flow, for example: source , load and conductor.

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

    Three basic conditions must exist to have a complete circuit so that electron may flow, for example, source, load and conductor.

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

    Short-circuit: A short circuit is simply a low resistance connection between the two conductors supplying electrical power to any circuit.

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

    Open circuit: A circuit in which the continuity is broken due to which the electric current can not flow

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

    closed circuit: A circuit is closed if the circle is complete if all current have a path back to where they came from.

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

    What is provided by a switch in a circuit? Switches control the flow of current through the load by opening the circuit and disconnecting the load from the source.

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

    Why are circuit breakers and fuses added to electrical circuits? Fuses or circuit breakers are added to circuit to protect electrical components from having too much current flow through them. Too much current can cause damage from excess heat, or mechanical damage due to strong magnetic fields.

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

    Which way does current flow from the source out through the load?

    1. current flows through loads from negative to positive
    2. current flows through sources from positive to negative.

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

    What is the difference between Direct current and Alternating current?

    1. Direct current: DC is current that flows in the same direction all the time, for example, batteries, thermocouples, photovoltaic cells, and DC generators. Alternating Current(AC): AC changes its direction continuously and at regular intervals

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

    What are the two common formulas used for determining power dissipation in resistive loads?

    1. P=E(2)/R
    2. P=I(2)*R

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

    You have a 3000 watt baseboard heater rated for 240 volts, determine the heaters resistance and how much current it draws when operating? R=E(2)/P E=240(2)/ P=3000 57600/3000=19.2 ohms R= 19.2 ohms

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

    A 240 volt electric dryer and the heating element draws 30 amps. Determine wattage the element develops and the resistance of the element? R=E/I 240/30= 8 ohms

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

    you have an electric frying pan rated for 1440 watts at 120 volts. Determine the maximum amps drawn by the electric frying pan and its resistance? R=E(2)/P 120(2)/1440 14400/1440= 10 ohms

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

    You have twelve 120 volt toasters that draw 11 amps each. What is the wattage developed by each toaster? What is the total wattage of all the toasters? What is the resistance of the element of each toaster? R=E/I 120/12=10 10/11=0.909 ohms or 120/11= 10.99 ohms

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

    Seven precautions when handling electrical measuring instruments?

    1. Never use a resistance measuring device on a live circuit.
    2. measuring resistance , make sure the current is off.
    3. voltmeters, ammeters, and watt meters require the circuit power to be on when taking measurements .
    4. match the meter to supply, this means that, if you are working with DC, use DC meter and if working with AC, used AC meter.
    5. Check that the meter is oriented correctly to be read, some meters are meant to be read with the meter sitting up, and others are meant to be read with the meter lying down.
    6. it is important that you read the meter looking straight at the pointer.
    7. looking at the meter from off to either side will introduce an error in reading known as parallax error.

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

    List the four things that should be observed when handling watt meters:

    1. connect the voltage coil in parallel with the load. Do not exceed the rating of voltage coil.
    2. connect the current coil in series with the load. Do not exceed the rating of the current coil.
    3. Do not exceed the power rating of the meter.
    4. we must observe the polarity of both coils. Otherwise, the meter pointer will try to deflect down below the zero of the scale and meter may be damaged.

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

    What is meant by VOM? Ans: Volt-Ohmmeter (VOM) is a network troubleshooting that measure voltage, amperage and resistance on a cable or other conductive element.

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

    What is a resistor? Ans: A resistor is an electrical component that introduces a specified amount of resistance into a circuit.

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

    How are resistors rated? Ans: Resistor are rated according to their resistance value and their wattage. As the watts rating of a resistor increases, so doe s its physical dimensions. Many of the color-coded resistor also have a tolerance rating.

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

    What are the three main classes of resistors?

    <p>a. fixed b. variable c. adjustable</p> Signup and view all the answers

    There are three main classes of fixed resistors:

    1. the wire-wound resistor
    2. the film resistor
    3. the carbon composition resistor

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

    carbon composition resistor: Red, Brown, Yellow and Gold: Red is 2, Brown is 1 , Yellow is Multiplier of 10 k and gold is +5% Ans: 210kohms+5% ( 210,000+5%)

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

    orange, orange, red and sliver: orange is 3 , orange is 3, red is multiplier of 10k and silver is +10% 330k+10%(33,000 +10%)

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

    yellow, yellow, sliver and gold: yellow is 4, yellow is 4 , silver is multiplier of 0.01 and gold is +5% 0.44ohms+5%

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

    How many terminals does a variable resistor have?

    <p>It has three terminals but use only 2 terminals</p> Signup and view all the answers

    The product of emf, current and time is:

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

    the product of emf and current is :

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

    the product of power and time is:

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

    How many kilowatt hours of energy does it require to operate a 1200 watt hair dryer for 10 minutes? (1200/100=1.2)(10 minutes/60 minutes=0.166666) 1.2*0.1666=

    <p>0.1999 or 0.2 kW/h</p> Signup and view all the answers

    If a 25 kW electric furnace operates for 3 hours in a 24-hour period, and the supply authority charges $ .07/kW/h, what does it cost each day to operate the furnace? (25 kW * 3 h)=75 *.07=5.25

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

    if an electric clothes dryer draws 30 A at 240 V and is operated for 45 minutes, what is the kW/h consumption? (30 A 240 V=7200) 45/60=0.75 M/H 7200/1000=7.2 kW 7.2 kW0.75 h=5.4 kW/h

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

    A 1500 W/240 V baseboard heater is operated for 15 minutes and a 1200 W/120 V baseboard heater is operated for 30 minutes. What is the combined kW/h consumption of the two heaters? At $.07 kW/h, what is the cost of operating the two heaters . solution 1: (1500 W/1000=1.5 kW) (15/60=0.25 kW) 1.5 *0.25=0.375 kW/h solution II: (1200 W/ 1000=1.2 kW)(30/60=0.5 h) 1.2 kW 0.5 h=0.6 kW/h 0.375+0.6=0.975 0.975.07= 0.068

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

    A device that changes electrical energy into other forms of energy is referred to as a

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

    A parallel path of low resistance is the definition of a

    <p>short-circuit</p> Signup and view all the answers

    Two main types of damage that are likely to occur because of excessively high current are

    <p>thermal and mechanical</p> Signup and view all the answers

    The term that refers to the charge at one point with respect to another point is

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

    A fuse or circuit breaker protects a circuit from excessive current by ..... the circuit when too much current flows through it.

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

    When a switch is in the open position, is it on or off? Ans: on

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

    current flows through the source from negative to positive

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

    The three necessary components of a circuit are the source, load and conductors

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

    To stop the load, the switch must be open.

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

    If it requires 120 volts to push current through a light bulb at the rate of 2.5 amperes , what is the power rating of the light bulb? and what is the resistance of the filament in the light bulb in the same question?

    <p>P=I<em>E (120</em>2.5=300 watts), R=E/I (120/2.5=48 ohms</p> Signup and view all the answers

    if a heater connected to a 240 V source of electromotive force draws a current of 3.125 amperes, what is the resistance of the heater ? R=V/I( 240/3.125=76.8 ohms)

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

    if the voltage applied to a circuit increases, the current through the circuit ....

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

    If the resistance of a circuit decreases, the current flowing through the circuit increases

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

    if the resistance of a circuit decreases, the power dissipated by the circuit increases. (power dissipated formular: p=V*I, p=I(2)*R, p=V(2)/R

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

    If the voltage applied to a circuit doubles, the power dissipated by the circuit increases by 4 times .

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

    The current running in an electric circuit is directly related to applied voltage and inversely proportional to the resistance of the circuit

    <p>ohm's law</p> Signup and view all the answers

    The power in a circuit is equal to the product of the voltage times the current in the circuit

    <p>watt's law</p> Signup and view all the answers

    express 13800 volts as kilovolts( 1 kilovolt=1000 volts )

    <p>13.8 kilovolts</p> Signup and view all the answers

    express 500 000 volts as megavolts. ( 1 milliamp=1000 microamperes

    <p>3.4 microamperes</p> Signup and view all the answers

    express 500 000 volts as megavolts ( 1 million volt= one megavolts ) (500 000/1 000 000)

    <p>0.5 megavolts</p> Signup and view all the answers

    if the voltage applied to an electric circuit is doubled, what happens to the current flowing through that circuit?

    <p>it will double</p> Signup and view all the answers

    express 18.2 microamperes ( 18.2/ 1 000 000)

    <p>0.0000182 A</p> Signup and view all the answers

    Express 470 kilohms as ohms( 470 kilohms *1000)

    <p>470 000 ohms</p> Signup and view all the answers

    express 27 000 000 microohms as kilohms( one billions microohms = one kilohms ( 27 000 000/ 1 000 000 000)

    <p>0.027 kilohms</p> Signup and view all the answers

    How many kilowatts are equal to 1500 watts ? ( 1000 milliwatt= one watt) ( 1500 * 1000=)

    <p>1.5 kilowatt</p> Signup and view all the answers

    express 1500 watts as milliwatts ( 1500 *1000= 1 500 000 milliwatts)

    <p>1 500 000 milliwatts</p> Signup and view all the answers

    What will happen if you connect a DC meter with wrong polarity?

    <p>The needle will deflect down below zero of scale and most likely it would damage the motor.</p> Signup and view all the answers

    Study Notes

    Basics of Electricity

    • Matter is made up of tiny particles called atoms, which are the building blocks of elements.
    • Elements with atoms that easily release electrons are called conductors.
    • Compounds have atoms of more than one type.

    Electricity Fundamentals

    • Energy cannot be created or destroyed, only converted from one form to another.
    • The unit of electric charge is the coulomb (C), and the unit of electric current is the ampere (A).
    • Electric charge flows from positive to negative terminal.

    Electric Circuits

    • A circuit is a path through which electrons flow, consisting of a source, load, and conductor.
    • A short circuit is a low-resistance connection between two conductors, while an open circuit is a broken connection that prevents electron flow.
    • A closed circuit is a complete path for electrons to flow from the source, through the load, and back to the source.

    Ohm's Law

    • Ohm's Law relates voltage (V), current (I), and resistance (R): V = I × R
    • Three forms of Ohm's Law: I = V/R, V = I × R, R = V/I
    • Power (P) is the rate at which work is done or energy is transformed: P = E × I or P = I² × R or P = V²/R

    Electrical Drawings

    • Four types of electrical drawings: pictorial, block diagram, wiring diagram, and schematic diagram
    • One-line diagrams show the highest voltage and are easy to understand, while block diagrams use blocks to represent components.

    Electromotive Force (EMF)

    • EMF is the driving force behind electric current, pushing electrons from one atom to another.
    • Six sources of EMF: friction, chemical, pressure, heat, light, and magnetism.

    Electricity Safety

    • Two hazards of electrostatic charge: lightning and fuel handling
    • Seven precautions when handling electrical measuring instruments, including not using resistance measuring devices on live circuits and matching meters to supply.

    Wattmeters and Voltmeters

    • Wattmeters measure power, voltmeters measure voltage, and ammeters measure current.
    • Four things to observe when handling wattmeters: connect voltage coil in parallel, connect current coil in series, do not exceed power rating, and observe polarity.

    Resistors

    • A resistor is an electrical component that introduces a specified amount of resistance into a circuit.
    • Resistors are rated by their resistance value and wattage rating.
    • Three main classes of resistors: wire-wound, film, and carbon composition.

    Variable Resistors

    • A variable resistor has three terminals.
    • A variable resistor is used to control the amount of resistance in a circuit.

    Electric Power

    • Electric power is the rate at which work is done or energy is transformed.
    • Electric power is measured in watts (W) and is calculated by the product of voltage and current.

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