JAMB and WAEC Physics questions

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

1. Question 661· Simple a.c. circuits· WAEC

   Find the reactance of a 0.7 H inductor on a 50 Hz supply. [π = 22/7]

   • A110 Ω
   • B220 Ω
   • C35 Ω
   • D440 Ω

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   Answer: B. 220 Ω

   Explanation and discussion

2. Question 662· Simple a.c. circuits· WAEC

   The frequency of the public electricity supply in Nigeria is

   • A50 Hz
   • B60 Hz
   • C100 Hz
   • D240 Hz

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   Answer: A. 50 Hz

   Explanation and discussion

3. Question 663· 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

4. Question 664· 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

5. Question 665· Simple a.c. circuits· WAEC

   An alternating current has a peak value of 10√2 A. Its r.m.s. value is

   • A10 A
   • B20 A
   • C14.1 A
   • D5 A

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   Answer: A. 10 A

   Explanation and discussion

6. Question 666· 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

7. Question 667· 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

8. Question 668· Simple a.c. circuits· WAEC

   The peak value of an alternating current is 10√2 A. Find its r.m.s. value.

   • A14.1 A
   • B20 A
   • C10 A
   • D5 A

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   Answer: C. 10 A

   Explanation and discussion

9. Question 669· Simple a.c. circuits· WAEC

   The unit of inductive reactance is the

   • Aohm
   • Bhenry
   • Cfarad
   • Dhertz

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   Answer: A. ohm

   Explanation and discussion

10. Question 670· 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

11. Question 671· 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

12. Question 672· 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

13. Question 673· Simple a.c. circuits· WAEC

    In a purely resistive a.c. circuit, the current and voltage are

    • A180° out of phase
    • B90° out of phase
    • Cin phase
    • Dalways zero

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    Answer: C. in phase

    Explanation and discussion

14. Question 674· Simple a.c. circuits· WAEC

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

    • Ais always zero
    • Bleads the voltage by 90°
    • Cis in phase with the voltage
    • Dlags the voltage by 90°

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    Answer: D. lags the voltage by 90°

    Explanation and discussion

15. Question 675· Simple a.c. circuits· WAEC

    The r.m.s. value of an a.c. voltage with peak 340 V is about

    • A240 V
    • B340 V
    • C480 V
    • D170 V

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    Answer: A. 240 V

    Explanation and discussion

16. Question 676· 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

17. Question 677· 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

18. Question 678· Simple machines· WAEC

    A pulley system of velocity ratio 3 lifts a load of 300 N with an effort of 125 N. Find its efficiency.

    • A2.4%
    • B80%
    • C120%
    • D60%

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    Answer: B. 80%

    Explanation and discussion

19. Question 679· Simple machines· WAEC

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

    • Athe effort is small
    • Bthe load is heavy
    • Csome energy is lost to friction
    • Dthe velocity ratio is large

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    Answer: C. some energy is lost to friction

    Explanation and discussion

20. Question 680· 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