JAMB Physics questions

450 questions with answers and explanations. Tap an option to check yourself.

1. Question 101· Electrical energy and power· JAMB

   A 60 W bulb is used on a 240 V supply. Find the current it draws.

   • A4 A
   • B0.25 A
   • C14 400 A
   • D0.5 A

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2. Question 102· Electrical energy and power· JAMB

   Find the resistance of a bulb rated 100 W, 220 V.

   • A0.45 Ω
   • B2.2 Ω
   • C484 Ω
   • D22 000 Ω

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3. Question 103· Electrical energy and power· JAMB

   A 2 kW heater is used for 3 hours. How much energy does it use?

   • A0.67 kWh
   • B6 kWh
   • C1.5 kWh
   • D6,000 kWh

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4. Question 104· Electrical energy and power· JAMB

   A 2 kW electric iron is used for 5 hours. If electricity costs ₦70 per kWh, find the cost.

   • A₦70
   • B₦140
   • C₦350
   • D₦700

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5. Question 105· Electrical energy and power· JAMB

   A 2.4 kW electric kettle is used on a 240 V supply. The most suitable fuse is

   • A13 A
   • B3 A
   • C5 A
   • D30 A

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6. Question 106· Electrical energy and power· JAMB

   A resistor gets hot when current flows because

   • Aelectrons collide with the atoms of the conductor
   • Bit is magnetic
   • Cit stores charge
   • Dit absorbs light

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7. Question 107· Electromagnetic induction· JAMB

   Faraday's law states that the induced e.m.f. is proportional to the

   • Arate of change of magnetic flux linkage
   • Bresistance of the coil
   • Ccurrent in the coil
   • Darea of the coil only

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8. Question 108· Electromagnetic induction· JAMB

   In a step-up transformer, the secondary coil has

   • Amore turns than the primary coil
   • Bfewer turns than the primary coil
   • Cthe same number of turns
   • Dno turns

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9. Question 109· Electromagnetic induction· JAMB

   A transformer has 200 turns in the primary and 1000 turns in the secondary. If the primary voltage is 40 V, the secondary voltage is:

   • A8 V
   • B400 V
   • C200 V
   • D5 V

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10. Question 110· Electromagnetic induction· JAMB

    A step-down transformer changes 240 V to 12 V. If the primary coil has 2000 turns, how many turns has the secondary?

    • A200
    • B40 000
    • C100
    • D20

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11. Question 111· Electromagnetic induction· JAMB

    An a.c. generator differs from a d.c. generator mainly in having

    • Ano coil
    • Bslip rings instead of a split-ring commutator
    • Cno magnet
    • Diron brushes

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12. Question 112· Electromagnetic induction· JAMB

    An a.c. generator converts

    • Achemical energy into electrical energy
    • Belectrical energy into mechanical energy
    • Cheat into light
    • Dmechanical energy into electrical energy

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13. Question 113· Electromagnetic induction· JAMB

    A transformer that is 90% efficient delivers 180 W. Find its input power.

    • A162 W
    • B200 W
    • C180 W
    • D270 W

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14. Question 114· Electromagnetic induction· JAMB

    The direction of an induced current is given by:

    • ALenz's law
    • BFleming's left-hand rule
    • COhm's law
    • DCoulomb's law

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15. Question 115· Electromagnetic induction· JAMB

    Energy losses due to eddy currents in a transformer core are reduced by

    • Ausing thicker wire
    • Blaminating the core
    • Cusing a solid iron core
    • Dincreasing the voltage

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16. Question 116· Electromagnetic induction· JAMB

    Faraday's law states that the induced e.m.f. in a circuit is proportional to the

    • Anumber of cells
    • Bstrength of the magnet only
    • Cresistance of the circuit
    • Drate of change of magnetic flux linkage

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17. Question 117· Electromagnetic induction· JAMB

    A transformer does not work with a steady direct current because

    • Ad.c. overheats the core
    • Bd.c. is too weak
    • Ca steady current produces no changing magnetic flux
    • Dthe coils would melt

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18. Question 118· Electromagnetic induction· JAMB

    A transformer works on the principle of

    • Amutual induction
    • Bself-induction only
    • Cthe heating effect of current
    • Delectrolysis

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19. Question 119· Electromagnetic induction· JAMB

    Electric power is transmitted over long distances at very high voltage mainly to

    • Amake the cables lighter
    • Bincrease the current
    • Creduce energy lost as heat in the cables
    • Dincrease the frequency

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20. Question 120· Electromagnetic induction· JAMB

    A transformer steps 240 V down to 12 V. If the secondary coil has 50 turns, the primary has

    • A2.5 turns
    • B1,000 turns
    • C20 turns
    • D50 turns

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