JAMB Physics questions: Simple a.c. circuits

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

1. Question 1· 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°

   Show answer

   Explanation and discussion

2. Question 2· 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

   Show answer

   Explanation and discussion

3. Question 3· 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

   Show answer

   Explanation and discussion

4. Question 4· 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

   Show answer

   Explanation and discussion

5. Question 5· 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

   Show answer

   Explanation and discussion

6. Question 6· 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

   Show answer

   Explanation and discussion

7. Question 7· 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

   Show answer

   Explanation and discussion

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

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

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

   Show answer

   Explanation and discussion