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Questions and Answers

What is a primary benefit of solar cells?

  • They can operate on solar radiation at no cost. (correct)
  • They emit harmful substances.
  • They have a short operational lifetime.
  • They are cost-effective to produce.

    • Solar cells are currently only used in clocks and calculators.

    False

    What are the two types of transistors mentioned?

    npn and pnp

    The three terminals of a transistor are known as the _____, _____, and _____.

    <p>emitter, collector, base</p> Signup and view all the answers

    Match each term related to transistors with its description:

    <p>Emitter = Terminal that emits carriers Collector = Terminal that collects carriers Base = Terminal that controls carrier flow pnp = Type of transistor with two p-type and one n-type regions</p> Signup and view all the answers

    Which statement about the lifetime of solar cells is true?

    <p>They have a long operational lifetime.</p> Signup and view all the answers

    Transistors can function with only one type of semiconductor junction.

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

    What is the role of the base terminal in a transistor?

    <p>To control the flow of carriers</p> Signup and view all the answers

    What is the outcome when using a bridge rectifier with four diodes on an alternating current?

    <p>Current is converted to direct current.</p> Signup and view all the answers

    When point X is positive relative to point Y, diodes D2 and D4 are forward biased.

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

    What apparatus is required to conduct the full wave rectification activity described?

    <p>Bicycle dynamo or an alternating current generator, four 1N 4001 diodes, a centre zero galvanometer, a 100 Ω rheostat, lead solder, and a soldering iron.</p> Signup and view all the answers

    In the full wave rectification activity, the galvanometer measures the _____ of current flowing in the circuit.

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

    Match the diode symbols with their correct functions:

    <p>D1 = Forward biased when X is positive D2 = Reverse biased when X is positive D3 = Forward biased when Y is negative D4 = Reverse biased when Y is negative</p> Signup and view all the answers

    Which component is adjusted to prevent the galvanometer's deflection from being too large?

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

    In an npn transistor, which terminal should be connected to the positive terminal?

    <p>Collector (C)</p> Signup and view all the answers

    What happens to the LED bulb when a 4.5 V battery is connected?

    <p>The bulb lights up with its normal brightness.</p> Signup and view all the answers

    In a pnp transistor, the collector is connected to the positive terminal.

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

    What is the primary function of a transistor?

    <p>Current amplifier</p> Signup and view all the answers

    The diodes in a bridge rectifier allow current to flow in both directions.

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

    In an npn transistor, current always flows from positive to _____ terminal.

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

    What is the function of the transistor in the circuit described?

    <p>To amplify current</p> Signup and view all the answers

    Match the transistor codes with their types:

    <p>2SC828 = NPN transistor 2SD400 = NPN transistor 2SC1061 = NPN transistor 2SD313 = NPN transistor</p> Signup and view all the answers

    A large current can be obtained as the output of the amplifier when a small AC current is supplied.

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

    What does the base-collector junction become when B is supplied a smaller potential difference in a npn transistor?

    <p>Reverse biased</p> Signup and view all the answers

    There is a common method to identify transistor terminals externally.

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

    What value of the volume controller (VR) is used in the circuit?

    <p>10 kΩ</p> Signup and view all the answers

    What is the function of the collector (C) in an npn transistor?

    <p>Receive current from the emitter</p> Signup and view all the answers

    The two bulbs used in the circuit are rated at _____ volts.

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

    Match the components with their functions in the circuit:

    <p>Transistor = Current amplification S1 = Input control L1 = Input bulb L2 = Output bulb</p> Signup and view all the answers

    Which switch is involved in the input circuit of the transistor amplifier?

    <p>S1</p> Signup and view all the answers

    When S1 is turned on and L1 begins to light up, S2 remains off.

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

    How many dry cells are required for the circuit?

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

    What component acts as a light sensor in the described switch circuit?

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

    The resistance of an LDR decreases in darkness.

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

    What is the purpose of the variable resistor (VR) in the circuit?

    <p>To adjust the resistance until the bulb lights up.</p> Signup and view all the answers

    When light is incident on the LDR, its resistance becomes approximately ______.

    <p>1 Ω</p> Signup and view all the answers

    Match the components with their roles in the circuit:

    <p>LDR = Light sensor D400 = Transistor VR = Variable resistor 2.5 V bulb = Indicator of light condition</p> Signup and view all the answers

    What happens to the bulb when the light falls on the LDR?

    <p>The bulb goes out</p> Signup and view all the answers

    Adjusting the VR can help the bulb light up when light intensity decreases.

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

    What is the total voltage across the LDR and VR in the circuit?

    <p>3 V</p> Signup and view all the answers

    What component is used to provide the forward biasing voltage to the base of the transistor?

    <p>22 kΩ resistor</p> Signup and view all the answers

    The 0.1 μF capacitor allows both alternating and direct signals to pass to the base.

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

    What is the purpose of the UM66 integrated circuit in the circuit described?

    <p>To produce a 'musical' audio frequency wave</p> Signup and view all the answers

    The forward biasing voltage required for the base of the transistor is _____ V.

    <p>0.7</p> Signup and view all the answers

    Match the components with their respective functions:

    <p>22 kΩ resistor = Provides forward biasing voltage 0.1 μF capacitor = Blocks direct current UM66 IC = Generates audio frequency signal Transistor = Acts as an electronic switch</p> Signup and view all the answers

    What is the operating voltage of the UM66 integrated circuit in the circuit?

    <p>3 V</p> Signup and view all the answers

    A transistor can serve as both a switch and an amplifier in electronic circuits.

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

    To hear an amplified output of the sound, small signals must be connected to points _____ and _____ of the amplifier circuit.

    <p>A, B</p> Signup and view all the answers

    Study Notes

    Electronics - Introduction

    • Electronics has a significant impact on daily life
    • Examples of electronic devices include mobile phones, computers, televisions, and radios

    Electrical Conductors and Insulators

    • Materials that conduct electricity are called conductors
    • Examples of conductors include copper, aluminum, iron, lead, brass, and nichrome
    • Materials that do not conduct electricity are called insulators
    • Examples of insulators include ebonite, polythene, plastic, dry wood, asbestos, and glass
    • The ability of electrons to move freely within a material is the reason for conductivity
    • Tightly bound inter-atomic (covalent) bonds in insulators prevent electron movement

    Semiconductors

    • Some materials conduct electricity to a small degree
    • These are called semiconductors; examples include silicon (Si) and germanium (Ge)
    • These elements have four electrons in their outer shell, forming a crystal lattice structure by sharing electrons in covalent bonds
    • Thermal energy breaks bonds, releasing electrons and creating vacancies (holes) in the lattice

    Properties of Intrinsic Semiconductors

    • Pure semiconductors are known as intrinsic semiconductors
    • The increase of temperature increases electron movement making current flow higher resulting in a decreased resistivity
    • The increase in temperature of semiconductors causes bonds to break, which creates more free electrons and holes resulting in increasing conductivity

    Extrinsic Semiconductors

    • Adding impurities to an intrinsic semiconductor to change its conductivity is called doping
    • Doping a semiconductor with group V elements (e.g., phosphorus) adds extra electrons creating n-type semiconductors
    • Doping with group III elements (e.g., boron) creates holes resulting in p-type semiconductors

    P-N Junction

    • A p-n junction is formed by joining p-type and n-type semiconductors
    • When a p-n junction is formed, electrons from the n-type region diffuse into the p-type region, and holes from the p-type region diffuse into the n-type region
    • The diffusion of these charge carriers creates a region near the junction devoid of charge carriers called the depletion layer or depletion region
    • This depletion layer forms a potential barrier

    Biasing a P-N Junction

    • Applying a potential difference across a p-n junction using an external source is called biasing
    • Forward biasing: Connecting the positive terminal to the p-region and the negative terminal to the n-region. This reduces the depletion layer width, allowing current to flow.
    • Reverse biasing: Connecting the negative terminal to the p-region and the positive terminal to the n-region. This increases the depletion layer width, preventing current flow.

    Rectification of Alternating Currents

    • The diodes allow current to flow in only one direction, converting alternating currents to direct currents

    Half-wave Rectification

    • In half-wave rectification, only half of the alternating current cycle is allowed to flow

    Full-wave Rectification

    • Using four diodes (a bridge circuit), both halves of the alternating cycle are utilized for current flow in one direction.

    Smoothing

    • Capacitors are used in parallel to reduce the voltage ripples in the rectified output voltage, creating a smoother direct current

    Transistors

    • A transistor is a semiconductor device composed of three regions: emitter, base, and collector
    • Two types of transistors are npn and pnp
    • Transistor action converts a small input current into a larger output current
    • Transistors amplify audio signals and are used in switching circuits as a switch

    Light Emitting Diodes (LEDs)

    • Light emitting diodes (LEDs) emit light when a current passes through them
    • LEDs are frequently used as indicators and in lighting applications

    Solar Cells

    • Solar cells are p-n junction devices that convert sunlight into electricity
    • They are composed of multiple p-n junctions working in series to generate voltages suitable for household application

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