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12th Physics - Current Electricity Model Question Paper 1 8682895000 Jan-06 , 2020

Current Electricity

12th Physics - Current Electricity Model Question Paper 1

Current Electricity Model Question Paper 1

12th Standard

    Reg.No. :
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Physics

Time : 01:00:00 Hrs
Total Marks : 50
    5 x 1 = 5

  1. A toaster operating at 240 V has a resistance of 120 Ω. The power is ______.

    (a)

    400 W

    (b)

    2 W

    (c)

    480 W

    (d)

    240 W

  2. Two wires of A and B with circular cross section made up of the same material with equal lengths. Suppose RA = 3 RB, then what is the ratio of radius of wire A to that of B?

    (a)

    3

    (b)

    \(\sqrt3\)

    (c)

    \(\frac{1}{\sqrt3}\)

    (d)

    \(\frac{1}{3}\)

  3. In a large building, there are 15 bulbs of 40 W, 5 bulbs of 100 W, 5 fans of 80 W and 1 heater of 1 kW are connected. The voltage of electric mains is 220 V. The maximum capacity of the main fuse of the building will be ______.

    (a)

    14 A

    (b)

    8 A

    (c)

    10 A

    (d)

    12 A

  4. Which of the following has negative temperature coefficient of resistance?

    (a)

    copper

    (b)

    tungsten

    (c)

    carbon

    (d)

    silver

  5. The temperature co-efficient of resistance for alloys is _____________.

    (a)

    low

    (b)

    very low

    (c)

    high

    (d)

    very high

    6. 5 x 2 = 10

  6. Define current density.

  7. Derive the expression for power P=VI in electrical circuit.

  8. What are free electrons?

  9. Define resistance.

  10. What do you mean by a series combination of cells?

    11. 5 x 3 = 15

  11. Consider a rectangular block of metal of height A, width B and length C as shown in the figure.

    If a potential difference of V is applied between the two faces A and B of the block (figure (a)), the current IAB is observed. Find the current that flows if the same potential difference V is applied between the two faces B and C of the block (figure (b)). Give your answers in terms of IAB.

  12. Two resistors when connected in series and parallel, their equivalent resistances are 15 Ω and \(\frac{56}{15}\)Ω respectively. Find the individual resistances.

  13. Calculate the equivalent resistance between A and B in the given circuit.

  14. In a circuit containing internal resistance r. Find the power delivered.

  15. Explain Peltier effect.

    16. 4 x 5 = 20

  16. Two electric bulbs marked 20 W – 220 V and 100 W – 220 V are connected in series to 440 V supply. Which bulb will get fused?

  17. A battery has an emf of 12 V and connected to a resistor of 3 Ω. The current in the circuit is 3.93 A. Calculate
    (a) terminal voltage and the internal resistance of the battery
    (b) power delivered by the battery and power delivered to the resistor

  18. A conductor of length I is connected to d.c. source of potential V. If the length of the conductor is doubled by treating it, keeping V constant, explain how do the following factors vary in the conductor
    (i) Drift velocity.
    (ii) Resistor
    (iii) Resistivity.

  19. Write mathematical relation between
    (i) mobility & drift velocity of charge carriers in a conductor
    (ii) mobility & relaxation time (or) mean free time.

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