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IAF Group X Physics Test - 4
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IAF Group X Physics Test - 4
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  • Question 1/10
    1 / -0

    In an electrical circuit, two resistors of 2 Ω and 4 Ω respectively are connected in series to a 6 V battery. The heat dissipated by the 4 Ω resistor in 5 s will be

    Solutions

    Current through the circuit is

    This current will flow through both resistors because of the series combination.

    Heat dissipated by 4Ω resistor is

    H = I2Rt = 12 4(5) = 20 J

     

  • Question 2/10
    1 / -0

    The wire used in the filaments of household bulbs has

    Solutions
    • As the resistance is less, heat energy is produced is very low which is not sufficient for an electric bulb to glow so the resistance is kept high
    • If the material has a high melting point so that it doesn't melt at the high temperature due to the high heat
    • The most commonly used wire in the filaments of a household bulb is tungsten(melting point = 3695 K)

    NOTE: Light bulb filaments aren't resistive because of the tungsten. They're resistive because of their very long length, and very thin wire.​

     

  • Question 3/10
    1 / -0

    An object is placed at a distance of 50 cm from a spherical mirror and its image is formed 10 cm behind the mirror. What is the focal length of the mirror?

    Solutions

    Given,

    The distance of the object from the mirror = u = -50 cm

    The distance of the image from the mirror = v = 10 cm

    To find the focal length (f)

    According to the mirror formula,

     

  • Question 4/10
    1 / -0

    The magnification of the lens is defined as the ratio of:

    Solutions

    Magnification of a lens is defined as the ratio of the height of the image to the height of the object.

    m = h′/h

    h' = Height of the image

    h = Height of the object

     

  • Question 5/10
    1 / -0

    At a given place the horizontal component of earth’s field is 0.2 G. If a vertical wire carries a current of 30 Amp upward, what is the magnitude and direction of the force on 1 meter of wire?

    Solutions

    F = BI l

    = 6 × 10-4 east to west

    the direction is given by left-hand rule

    earth's magnetic field is from south to north (forefinger)

    current is upwards (middle finger)

    force (west to east given by thumb)

     

  • Question 6/10
    1 / -0

    A coil is connected to 5Ω resistance load. Calculate the current flowing through the coil if the magnetic flux through the coil changes from 95 Wb to 65 Wb in 2 seconds.

    Solutions

    Current flowing through the coil is given as -

    i = e/R

    Where ‘e’ is induced emf and R is load resistance.

    Induced emf(e) is -

     

  • Question 7/10
    1 / -0

    What should be the core of an electromagnet?

    Solutions

    An electromagnet is a temporary magnet which should ideally have the property to behave as a magnet when current passes through it and lose magnetism as soon as current is stopped.

    Soft iron is generally used for making electromagnets because it has high magnetic permeability, i.e. it can easily gain magnetic properties when current is passed around the core and quickly lose when current is stopped.

    The soft iron inside the coil makes the magnetic field stronger because it becomes a magnet itself when the current is flowing

     

  • Question 8/10
    1 / -0

    The core used in transformers and other electromagnetic device is laminated to

    Solutions

    A magnetic core is a piece of magnetic material with a high magnetic permeability used to confine magnetic devices such as electromagnets, transformers etc.

    Eddy currents are loops of electrical current induced within conductors by a changing magnetic field.

    The core is laminated to reduce eddy current to a minimum as they interfere with the efficient transfer of energy from the primary coil to the secondary one.

    The eddy currents cause energy to be lost from the transformer as they heat up the core - meaning that electrical energy is being wasted as unwanted heat energy.

     

  • Question 9/10
    1 / -0

    1n0 + 235U92 → 140Ba56 + yKr36 + 31ng. Find y from the given fission equation of a uranium nucleus?

    Solutions

    During a fission reaction, net mass is balanced,

    Total mass of reactants = Total mass of products

    235 + 1 = 140 + y + 3(1)

    236 - 140 - 3 = y

    y = 93

     

  • Question 10/10
    1 / -0

    The function of LC tuned circuit used in a receiver is –

    Solutions

    The function of LC tuned circuit is to tune a radio to a particular station. The LC circuits are set at resonance for that particular carrier frequency.

     

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