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Physics Test 12
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Physics Test 12

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  • Question 1/8
    4 / -1

    A cylindrical conductor has uniform cross-section. Resistivity of its material increases from left end to right end linearly. Left end of the conductor is maintained at zero potential and right end is at V0. If at a distance x from left end, potential is equal to V, which of the following graphs. is correct

    Solutions

    At a distance x from left end, consider an infinitesimal small element of length dx. If potential difference across length dx is dV then 

    Hence, the graph between V and x will be parabola passing through origin and having increasing slope.

     

  • Question 2/8
    4 / -1

    Two resistances r1 and r2 are connected in parallel. The equivalent resistance is

    Solutions

    Two resistances r1 and r2 are connected in parallel. The equivalent resistance is find as above

     

  • Question 3/8
    4 / -1

    For the higher sensitivity which of the following is essential for the potentiometer ?

    Solutions

    For higher sensitivity of potentiometer, the value of gradient along the potentiometer wire should be small which is possible by increasing length of potentiometer wire.

     

  • Question 4/8
    4 / -1

    In the circuit shown in figure. The steady state currents i1 and i2 in the coils after the switch S is closed are:

    Solutions

     

  • Question 5/8
    4 / -1

    Two rails of a railway track insulated from each other and the ground are connected to a milli voltmeter. What is the reading of voltmeter, when a train travels with a speed of 180 km/hr along the track. Given that the vertical component of earth’s magnetic field is 0.2×10–4 weber/m and the rails are separated by 1 metre.

    Solutions

     

  • Question 6/8
    4 / -1

    When the current changes from + 2A to – 2A in 0.05 second, an e.m.f. of 8 V is induced in a coil. The coefficient of self-induction of the coil is

    Solutions

     

  • Question 7/8
    4 / -1

    The forbidden energy band gap in conductors, semiconductors and insulators are EG1, EG2 and EG3 respectively. The relation among them is

    Solutions

    In insulators, the forbidden energy gap is very large, in case of semiconductor it is moderate and in conductors the energy gap is zero.

     

  • Question 8/8
    4 / -1

    Two identical induction coils each of inductance L joined in series are placed very close to each other such that the winding direction of one is exactly opposite to that of the other. The net inductance is

    Solutions

    When the two coils are joined in series such that the winding of one is opposite to the other, then the emf produced in first coil is 180o out of phase of the emf produced in second coil. 
    Thus, emf produced in first coil is negative and the emf produced in second coil is positive so, net inductance is 

     

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