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سرکٹ اور برقی مقناطیسی امالہ

Written by Dr. Hamza Farooq (Physics)

ایم ڈی کیٹ · طبیعیات · 7 سوالات

نام: ____________________   تاریخ: ____________

  1. A cell of emf 12 V and internal resistance 1 ohm is connected to a 5 ohm resistor. What current flows?

    • A 12 A
    • B 2.4 A
    • C 2 A
    • D 6 A

  2. A Wheatstone bridge is balanced when:

    • A P / Q = R / S
    • B P + Q = R + S
    • C P x Q = R x S
    • D P = S

  3. Which law gives the direction of an induced current?

    • A Ampere's law
    • B Coulomb's law
    • C Lenz's law
    • D Ohm's law

  4. A transformer has 100 turns in the primary and 500 turns in the secondary. If the input is 20 V, what is the output voltage?

    • A 4 V
    • B 500 V
    • C 20 V
    • D 100 V

  5. Eddy currents are:

    • A Loops of current induced in a conductor by a changing magnetic flux
    • B Currents in a battery
    • C Currents that flow only in insulators
    • D Currents in a vacuum

  6. The SI unit of resistivity is the:

    • A Ohm
    • B Ohm metre
    • C Ohm per metre
    • D Siemens

  7. How much power is lost as heat when a current of 2 A flows through a wire of resistance 5 ohm?

    • A 10 W
    • B 40 W
    • C 20 W
    • D 2.5 W

جوابی کلید

1. C, 2. A, 3. C, 4. D, 5. A, 6. B, 7. C

  1. I = emf / (R + r) = 12 / (5 + 1) = 2 A.

  2. At balance, the ratio of resistances in one arm equals the ratio in the other, and no current flows through the galvanometer.

  3. Lenz's law says the induced current opposes the change in flux that produces it.

  4. Vs / Vp = Ns / Np, so Vs = 20 x 500 / 100 = 100 V.

  5. A changing magnetic flux induces circulating currents inside a solid conductor. These cause heating.

  6. Resistivity = R x A / L, whose unit is ohm metre.

  7. P = I² R = 4 x 5 = 20 W.