JAMB Physics questions

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

1. Question 361· Simple a.c. circuits· JAMB

   In a purely capacitive a.c. circuit, the current

   • Ais zero
   • Blags behind the voltage by 90°
   • Cis in phase with the voltage
   • Dleads the voltage by 90°

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   Answer: D. leads the voltage by 90°

   Explanation and discussion

2. Question 362· Simple a.c. circuits· JAMB

   The reactance of a capacitor in an a.c. circuit

   • Adoes not depend on frequency
   • Bincreases as the frequency increases
   • Cdecreases as the frequency increases
   • Dis always zero

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   Answer: C. decreases as the frequency increases

   Explanation and discussion

3. Question 363· Simple a.c. circuits· JAMB

   An inductor in an a.c. circuit

   • Aopposes changes in the current through it
   • Bstores charge on plates
   • Cconverts a.c. to d.c.
   • Dhas no effect

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   Answer: A. opposes changes in the current through it

   Explanation and discussion

4. Question 364· Simple a.c. circuits· JAMB

   Find the peak voltage of a 230 V r.m.s. supply.

   • A230 V
   • B163 V
   • C325 V
   • D460 V

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   Answer: C. 325 V

   Explanation and discussion

5. Question 365· Simple a.c. circuits· JAMB

   The reactance of an inductor in an a.c. circuit increases when the frequency

   • Adecreases
   • Bincreases
   • Cis kept constant
   • Dfalls to zero

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   Answer: B. increases

   Explanation and discussion

6. Question 366· Simple a.c. circuits· JAMB

   The r.m.s. value of the mains supply is 240 V. Find its peak value.

   • A480 V
   • Babout 170 V
   • C240 V
   • Dabout 339 V

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   Answer: D. about 339 V

   Explanation and discussion

7. Question 367· Simple a.c. circuits· JAMB

   An alternating voltage has a peak value of 10√2 V. Find its r.m.s. value.

   • A5 V
   • B20 V
   • C14.1 V
   • D10 V

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   Answer: D. 10 V

   Explanation and discussion

8. Question 368· Simple a.c. circuits· JAMB

   The frequency of the mains a.c. supply in Nigeria is

   • A100 Hz
   • B60 Hz
   • C220 Hz
   • D50 Hz

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   Answer: D. 50 Hz

   Explanation and discussion

9. Question 369· Simple machines· JAMB

   A wheel and axle has a wheel of radius 40 cm and an axle of radius 8 cm. Find its velocity ratio.

   • A32
   • B5
   • C0.2
   • D320

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   Answer: B. 5

   Explanation and discussion

10. Question 370· Simple machines· JAMB

    A windlass has a handle of radius 60 cm turning an axle of radius 12 cm. Its velocity ratio is

    • A48
    • B5
    • C72
    • D0.2

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    Answer: B. 5

    Explanation and discussion

11. Question 371· Simple machines· JAMB

    A pulley system with velocity ratio 4 lifts a load of 200 N with an effort of 80 N. Find its efficiency.

    • A160%
    • B40%
    • C80%
    • D62.5%

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    Answer: D. 62.5%

    Explanation and discussion

12. Question 372· Simple machines· JAMB

    A block and tackle with four pulleys has a velocity ratio of

    • A4
    • B2
    • C8
    • D1

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    Answer: A. 4

    Explanation and discussion

13. Question 373· Simple machines· JAMB

    A machine lifts a load of 600 N with an effort of 200 N. Find its mechanical advantage.

    • A0.33
    • B400
    • C3
    • D800

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    Answer: C. 3

    Explanation and discussion

14. Question 374· Simple machines· JAMB

    A screw jack has a pitch of 0.5 cm and a handle of length 35 cm. Find its velocity ratio. (Take π = 22/7.)

    • A70
    • B220
    • C440
    • D110

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    Answer: C. 440

    Explanation and discussion

15. Question 375· Simple machines· JAMB

    A wheelbarrow is a lever of the

    • Asecond class, with the load between the effort and the fulcrum
    • Bfirst class, with the fulcrum in the middle
    • Cthird class, with the effort in the middle
    • Dfourth class

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    Answer: A. second class, with the load between the effort and the fulcrum

    Explanation and discussion

16. Question 376· Simple machines· JAMB

    A third-class lever is one in which

    • Athe fulcrum is between the effort and the load
    • Bthe effort is between the fulcrum and the load
    • Cthe load is between the fulcrum and the effort
    • Dthere is no fulcrum

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    Answer: B. the effort is between the fulcrum and the load

    Explanation and discussion

17. Question 377· Simple machines· JAMB

    An inclined plane is 5 m long and raises a load through a height of 1 m. Find its velocity ratio.

    • A0.2
    • B5
    • C4
    • D6

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    Answer: B. 5

    Explanation and discussion

18. Question 378· Simple machines· JAMB

    An inclined plane 5 m long raises a load through a height of 1 m. Its velocity ratio is

    • A0.2
    • B5
    • C6
    • D4

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    Answer: B. 5

    Explanation and discussion

19. Question 379· Simple machines· JAMB

    The efficiency of a real machine is always less than 100% because

    • Athe load is too heavy
    • Bsome work is wasted in overcoming friction
    • Cthe effort is too small
    • Dmachines create energy

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    Answer: B. some work is wasted in overcoming friction

    Explanation and discussion

20. Question 380· Simple machines· JAMB

    A machine with velocity ratio 5 has an efficiency of 80%. Its mechanical advantage is:

    • A6.25
    • B5
    • C4
    • D0.16

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    Answer: C. 4

    Explanation and discussion