1. The diagram of FIGURE 1 represents a meter shunted by a parallel resistance Rs.(a) Determine the...

Question

1. The diagram of FIGURE 1 represents a meter shunted by a parallel resistance Rs.
(a) Determine the required value of the shunt resistance if the maximum value of the current I is 200 A. The meter can read a maximum of 1 mA and has a resistance of 0.1 Q.
s Rs Shunt
FIG. 1
(b) If the shunt is made of copper and has a cross-sectional area of
25 cm2 calculate its required length. (For copper take p as 1.7 x 10-8 Om.) 2. The circuit of FIGURE 2 shows a 10 kL2 potentiometer with a 5 ka load. Determine the position of the slider on the 9V 10 K2 `pot' when the voltage across points `XX' is 3 V. skit
FIG. 2
3. (a) Calculate the value of the current through the 12 V battery shown in FIGURE 3.
(b) Calculate the power dissipated in R1, R2 and R.

005_vnuyazo-t2gppufe.docx

Robert · Accepted Answer

Solution :
1.a   Since Rm and Rs are in parallel combination . current in meter can be written by using          
current divider formula. 
      
 
     

Where I is total current which is 200A in this problem and Im= 1mA.
So the required shunt resistance will be
      
     
 

   

   

          
  
   

   

   
       
   
   
         

So required shunt resistance is                    
1.b  we know the resistance formula  
      
 
 

Where ρ is resistivity of material which is 1.7*10-8 Ωm for above problem  
And A is area which is 25 cm2 for above problem 
l is length  of conductor
so the of conductor will be  
    
 
 

        

 So required length is
 
Lets assume the resistance of XX of potentiometer be Rx 
Therefore Rx and 5kΩ are in parallel   
So the 9 V will divided between( 10kΩ-Rx)  and parallel combination of Rx and 5kΩ 
Voltage across XX will be  
      
           
                   

      
  
      
      
      
      
          

  
         
                            

So 
          Rx will be 5000Ω or -10000Ω as negative value is not possible Rx will be 5000Ω 
Since the pot position is proportional  to resistance.

1. The diagram of FIGURE 1 represents a meter shunted by a parallel resistance Rs. (a) Determine the required value of the shunt resistance if the maximum value of the current I is 200 A. The meter...

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