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    Worksheet XII - 2 - Current Electricity

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    Parbhakar Kumar Bharduwas

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    © All Rights Reserved
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    Worksheet XII - 2 - Current Electricity

    Uploaded by

    Parbhakar Kumar Bharduwas
    2 views2 pages

    Original Title

    Worksheet XII - 2 -Current Electricity (1)

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    2 views2 pages

    Worksheet XII - 2 - Current Electricity

    Uploaded by

    Parbhakar Kumar Bharduwas

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 2

    AL YASMIN INTERNATIONAL SCHOOL,RIYADH

    (PEEVEES SCHOOLS, K.S.A)


    Affiliated to CBSE – New Delhi.

    PHYSICS
    WORKSHEET – 2

    Class: XII CURRENT ELECTRICITY

    1. Define electric current.


    2. Define current density.
    3. Define the term drift velocity and relaxation time. Obtain a relation between them.
    4. Derive an expression for the resistivity of a good conductor in terms of relaxation time of
    electrons.
    5. Derive the relation between current density and drift velocity of electrons inside a conductor.
    6. What is the effect of temperature on the resistivity of (i) metals, (ii) alloys, (iii)
    semiconductors, (iv) electrolytes?
    7. What are colour codes of carbon resistors?
    8. Define an electric cell.
    9. What is the emf of a cell? On what factors does it depend?
    10. What is internal resistance of a cell? On what factors does it depend?
    11. Three resistances R1,R2 and R3 are connected in (i) series and (ii) parallel. Find the equivalent
    resistance in each case.
    12. Discuss the combination of cells in series. Find the expression for total current. What will be
    the value of current, if
    (i) the cells are of very small internal resistance?
    (ii) the internal resistance of the cells is very high?
    13. Discuss the combination of cells in parallel. Find the expression for total current. What will
    be the value of current, if
    (i) the cells are of very small internal resistance?
    (ii) the internal resistance of the cells is very high?
    14. State and explain Kirchhoff’s laws of current distribution in an electric network.
    15. What is Wheatstone’s bridge? Derive the required conditions for the balanced Wheatstone’s
    Bridge.
    16. Draw a circuit diagram of a metre bridge arranged to determine an unknown resistance.
    Explain the principle of the experiment and give the formula used.
    17. How will you compare two resistances using a metre bridge? Give the formula used.
    18. What is the principle of potentiometer? Why is it better than the other voltage measuring
    instruments? How can its sensitivity be increased?
    19. With the help of a circuit diagram explain how will you compare the emfs of two primary
    cells using a potentiometer.
    20. With the help of a circuit diagram explain how will you measure the internal resistance of a
    cell using a potentiometer. Derive the formula used.
    21. How does a heating wire differ from a fuse wire?
    22. Define the term drift speed and relaxation time.
    23. Define electric conductivity of a metal. How is it related with j,the current density and E, the
    intensity of electric field along the wire? Derive Ohm’s law on the basis of this relation.
    24. Determine the equivalent resistance of the network shown in figure.
    25. A storage battery of emf 8V and internal resistance 0.5 Ω is being charged by a 120V d.c.
    supply using a series resistor of 15.5 Ω. What is the terminal voltage of the battery during
    charging? What is the purpose of having a series resistor in the charging circuit?
    26. Determine the current in each branch of the network shown in figure.
    27. The reading of a high resistance voltmeter, when a cell is connected across it, is 2.2V. When
    the terminals of the cell are also connected to a resistance of 5Ω as shown in the circuit, the
    voltmeter reading drops to 1.8V. Find the internal resistance of the cell.
    28. Find the value of unknown resistance X, in the following circuit, if no current flows through
    the section AD. Also calculate the current drawn by the circuit from the battery of emf 6V and
    negligible internal resistance.
    29. Use Kirchhoff’s laws to determine the value of current I1 in the electrical circuit given below.
    30. Two cells of emf 1.5 V and 2 V have internal resistances 1Ω and 2Ω respectively are
    connected in parallel to pass a current in the same direction through an external resistance of 5Ω.
    (i)Draw the circuit diagram.
    (ii)Using Kirchhoff’s laws, calculate the current through each branch of the circuit and potential
    difference across 5Ω resistor.

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