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    Podar International School, Ambegaon STD: Vii Subject: Science

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    Aarush Pandey
    Here is a labeled diagram of an electric bell: [DIAGRAM OF ELECTRIC BELL WITH LABELS FOR BATTERY, SWITCH, ELECTROMAGNET, ARMATURE, HAMMER AND BELL] The main components of an electric bell are: - Battery - Provides electric current to the circuit - Switch - Used to open and close the circuit - Electromagnet - Produces a magnetic field when current passes through it - Armature - Attracted by the electromagnet when it is energized - Hammer - Attached to the armature and hits the bell to produce sound - Bell - Rings when struck by the hammer When

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    Podar International School, Ambegaon STD: Vii Subject: Science

    Uploaded by

    Aarush Pandey
    1K views6 pages
    Here is a labeled diagram of an electric bell: [DIAGRAM OF ELECTRIC BELL WITH LABELS FOR BATTERY, SWITCH, ELECTROMAGNET, ARMATURE, HAMMER AND BELL] The main components of an electric bell are: - Battery - Provides electric current to the circuit - Switch - Used to open and close the circuit - Electromagnet - Produces a magnetic field when current passes through it - Armature - Attracted by the electromagnet when it is energized - Hammer - Attached to the armature and hits the bell to produce sound - Bell - Rings when struck by the hammer When

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    Here is a labeled diagram of an electric bell: [DIAGRAM OF ELECTRIC BELL WITH LABELS FOR BATTERY, SWITCH, ELECTROMAGNET, ARMATURE, HAMMER AND BELL] The main components of an electric bell are: - Battery - Provides electric current to the circuit - Switch - Used to open and close the circuit - Electromagnet - Produces a magnetic field when current passes through it - Armature - Attracted by the electromagnet when it is energized - Hammer - Attached to the armature and hits the bell to produce sound - Bell - Rings when struck by the hammer When

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    1K views6 pages

    Podar International School, Ambegaon STD: Vii Subject: Science

    Uploaded by

    Aarush Pandey
    Here is a labeled diagram of an electric bell: [DIAGRAM OF ELECTRIC BELL WITH LABELS FOR BATTERY, SWITCH, ELECTROMAGNET, ARMATURE, HAMMER AND BELL] The main components of an electric bell are: - Battery - Provides electric current to the circuit - Switch - Used to open and close the circuit - Electromagnet - Produces a magnetic field when current passes through it - Armature - Attracted by the electromagnet when it is energized - Hammer - Attached to the armature and hits the bell to produce sound - Bell - Rings when struck by the hammer When

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    of 6

    PODAR INTERNATIONAL SCHOOL , AMBEGAON

    STD: VII SUBJECT: SCIENCE

    Topic: Electricity and its effects

    Electric Current

    Q1: Define the term ‘electric current’ and state its unit.

    Ans: The rate of flow of charges through an electric conductor (a material which
    allows electrical charges to flow through it) is called an electric current. The SI
    unit of measurement of electrical current is called ampere (A).

    Q2: What do you understand by ‘potential difference’? State its SI unit.

    Ans: Potential difference is defined as the amount of work done to move a unit
    charge from one point to another. The SI unit to measure the potential
    difference is called volt (V).

    Electric circuit

    Q3: Define an electric circuit.

    Ans: The complete path from one terminal of an electric cell through the bulb
    and back to the other terminal of the electric cell is called electric circuit.

    Components of an electric circuit

    Q4: Name the components of an electric circuit.

    Ans: The four basic components of an electric circuit are: source of the electric
    current like cells, connecting wires, appliance like bulb and a switch.

    Q5: Explain the formation and uses of battery.

    Ans: When two cells are joined together via conducting wires in such a way
    that the positive end of one cell is joined to the negative end of the other cell,
    the arrangement is called a battery.

    It is used to apply a large potential difference between two ends of a conductor.


    Q6: What is an electric switch?

    Ans: It is a device used for making or breaking a circuit

    Q7: Draw diagrams showing open and closed circuits.

    Q8: What is the utility of a resistor in a circuit?

    Ans: It is a two terminal electrical component that is used in electric circuits to


    reduce the flow of electric current. A resistor offers obstacles in the path of flow
    of electric current, and thereby it reduces the flow of electric current. Through
    this device, the flow of electric current in a circuit can be controlled.

    Q9: What are connecting wires in a circuit made up of and why?

    Ans: Connecting wires in a circuit are made of metals like copper and
    aluminium. They are made up of metals because metals are good conductors of
    electricity and allow electric current to pass through them.

    Q10. What does LED stand for?

    Ans: LED stands for Light Emitting Diode.

    Q11. What is a circuit diagram? Draw the symbols used for electric bulb,
    cell, battery, open switch and closed switch.

    Ans: An illustration of an electrical circuit with such standard symbols is


    known as a circuit diagram.
    Measuring Devices

    Q12: What is an ammeter and state its use.

    Ans: A device is required to measure the amount of electric current flowing


    through a circuit. This device is called ammeter, and it measures electric
    current in amperes.

    Q13: What is the use of a voltmeter?

    Ans: Voltmeter measures the potential difference between two points in the
    voltage.

    Heating Effect of Electric current

    Q14: Why does electric current show heating effect?

    Ans: When an electric current flows through a wire, a part of the electrical
    energy gets converted into heat energy, and the wire gets heated. This is known
    as the heating effect of an electric current.

    Q15: State the factors on which amount of heat produced depends?

    Ans: The amount of heat produced by the flow of current through a wire
    depends upon the following factors:

    Material of the wire

    • Thickness of the wire

    • Length of the wire

    • Amount of the current flow


    Q16: What do you understand by ‘lightning effect of electric current’?

    Ans: When electric current is passed through a conductor, it becomes very hot
    due to which it emits light. This is called lighting effect of electric current. For
    example: electric bulbs, fluorescent lamps, etc.

    Q17: An electrician is carrying out some repairs in a building. He wants to


    replace a fuse by a piece of wire. Would you agree with the electrician?
    Give reasons for your response.

    Ans: No, the electrician should not be allowed to replace the fuse in the house
    with a piece of wire.

    This is because every wire cannot be used as a fused filament. A fuse filament
    must have a low melting point such that it could melt and break in response to
    a large amount of current. Most of the wires have high melting points and
    hence a wire cannot be used to replace the fuse.

    Q18: What does MCB stand for and what is its use?

    Ans: MCB stands for Miniature Circuit Breaker. It is a switch that


    automatically stops the current in a circuit if the current in it exceeds the
    specified maximum limit.

    Magnetic effect of Electric Current

    Q19: Define magnetic field?

    Ans: The region in the vicinity of a magnet, where force of attraction or


    repulsion can be felt by magnetic materials, is called a magnetic field.

    Q20: What is a solenoid?

    Ans: A solenoid is a cylindrical coil of a metal wire. Commonly, a solenoid is


    made by coiling a metal wire on the hollow cylindrical plastic or ceramic tube
    (called core). When current passes through a solenoid, it starts to behave like a
    bar magnet.

    Q21: How can we increase the strength of the magnetic field in a


    solenoid?

    Ans: The strength of the magnetic field of a solenoid can be increased in three
    ways:

    • Increasing the number of turns of the coil of the solenoid.


    • Replacing the cylindrical core with soft iron cylinder.

    • Increasing the amount of current flowing through the solenoid.

    Q22: When the current is switched on through a wire, a compass needle


    kept nearby gets deflected from its north-south position. Explain.

    When current is passed through the wire, it deflects the compass near it from
    its north-south position like a magnet. This is called magnetic effect of the
    current. As we know that needle of the compass is made up of a thin magnet.
    When this needle comes in contact with another magnet then the like poles of
    the magnet repel each other and opposite poles attract each other. So, the
    deflection is seen in the needle. In this case the wire behaves like a magnet and
    causes deflection in needle of the compass.

    Electromagnet

    Q23: State any three uses of electromagnets.

    Ans: Electromagnets are used in various electrical appliances such as electric


    bell, electric fan, electric motor etc.

    • Electromagnets are also used for the preparation of strong permanent


    magnets.

    • Doctors use very small electromagnetic devices to take out small magnetic
    materials from eyes, ears and nose.

    • Very strong electromagnets are used for magnetic separation of iron ores.

    Electric Bell

    Q24: Draw a neat and well labeled diagram of an electric bell.

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