Simple A. C. Circuits - Jamb Physics Past Questions and Answers

Question 41:

• JAMB 2017

Which of the following operations can be used to convert an alternative current dynamo into a direct current dynamo

A. Number of turns in the coil is increased
B. Strength of the field magnet is increased
C. Slip rings are replaced with split ring cummutator
D. Coil is wound on a soft iron armature

Question 42:

• JAMB 2018

In a series R-L-C circuit at resonance, the voltages across the resistor and the inductor are 30V and 40V respectively. What is the voltage across the capacitor?

A. 30V
B. 70V
C. 50V
D. 40V

Question 43:

• JAMB 2019

Which of the following equations is the correct definition of the reactance of an indicator L?

A. Reactance = (Amplitude of voltage) \(\div\) (Amplitude of current)
B. Reactance = (Amplitude of voltage) x (Amplitude of current)
C. Reactance = (Amplitude of current)\(^2\) \(\div\) (Amplitude of voltage)
D. Reactance = (Amplitude of current)\(^2\) \(\div\) (Amplitude of voltage)\(\frac{1}{2}\)

Question 44:

• JAMB 2019

An alternating current can induce voltage because it has

A. Ripple value
B. Varying magnetic field
C. Weaker magnetic field than direct current
D. High peak value

Question 45:

• JAMB 2019

An a.c of 1A at a frequency of 800 cycles per second flows through a coil, the inductance of which is 2.5mH and the resistance of which is 5Ω. What is the power absorbed in the Coil?

A. 5W
B. 6W
C. 7W
D. 8W