Basic Electronics Paper 2, WASSCE (SC), 2023

Question 4

 

(a) State:
(i) how the range of a voltmeter can be extended.
(ii) two advantages of a moving-coil instrument.

(b) A moving-coil instrument having a coil of resistance 100 Ω requires a current of 1 mA to give a full scale deflection.
(i) Calculate the value of the series resistor required for the instrument to have a range of 0 - 200 V.
(ii) Draw the circuit diagram of the arrangement.

OBSERVATION

(a)        (i) The range of a voltmeter can be extended by connecting a high resistance known as multiplier in series with the instrument.

        (ii)           Advantages of a moving-coil instrument.

  • High sensitivity.
  • Even scale or uniform scale.
  • Unaffected by stray magnetic fields.
  • Low power consumption.
  • No hysteresis loss

                                                   
(b)     Given a moving-coil instrument with:
resistance = 100 Ω;
current = 1 mA to give a full-scale deflection.
(i) Value of the series resistor required for the instrument to have a range of 0 - 200 V.
                                                   

                                          

Value of series resistor
                                                      Rm =       
                        OR                 
                                                       = 199,900 Ω   
=199.9 k Ω                                                           =199.9 k Ω

                                        
(ii)          Circuit diagram of the arrangement.                             
Text Box: 200 VText Box: VText Box: OR              

Many of the candidates attempted this question Only few of those who attempted the question did not do the question correctly Many did not put unit for the answer.