Voltage Measuring Device has Non Infinite Resistance

Materials Required 

  • Carbon resistors of 10 kilo Ω
  • Cell
  • Key
  • Voltmeter
  • Connecting wires

 

Procedure 

Real Lab Procedure

                                             Figure: Circuit diagram

  • Take a voltmeter. Note the least count and zero error of the voltmeter.
  • Connect cell, key, carbon resistors of 10-kilo ohm, and voltmeter as shown in the figure.
  • Connect the voltmeter parallel to one of the carbon resistors.
  • Switch on the cell.
  • Close key.
  • Note voltmeter reading.
  • Calculate the resistance of the voltmeter using the equation.

Rv = resistance of voltmeter

V = voltmeter reading 

R = resistance of carbon resistors

E = voltage of the cell

  • Repeat the experiment by varying the value of E.

Simulator Procedure

  • To see the circuit diagram, click on the ‘Show circuit diagram’ check box shown inside the simulator window.
  • Connections can be made, as seen in the circuit diagram, by clicking and dragging the mouse from one connecting terminal to the other connecting terminal of the devices to be connected.
  • Drag wire from the positive terminal of the voltmeter to A carbon resistors of 10 kΩ.
  • Drag wire from the negative terminal of the voltmeter to B carbon resistors of 10 kΩ.
  • Drag wire from the positive terminal of the cell to A carbon resistors of 10 kΩ. 
  • Drag wire from the negative terminal of the cell to the key holder. 
  • Drag wire from key holder to C carbon resistors of 10 kΩ.
  • Drag and drop the key into the key holder.
  • Click on the Next button.
  • Drag and drop the key into the key holder.
  • In Voltmeter 1, select the option for cell values from the drop-down list.
  • Click on the Next button.
  • Click on the next button after referring to the observation table.
  • Drag and drop the key into the key holder.
  • In Voltmeter 2, select the option for cell values from the drop-down list.
  • Click on the Next button.
  • Click on the next button after referring to the observation table.
  • Drag and drop the key into the key holder.
  • In Voltmeter 3, select the option for cell values from the drop-down list.
  • Click on the Next button.
  • Click on the Reset button to do the experiment again.   

 

Observations and Calculations

 
Sl.No 
                  
                  

E = voltage of the cell 

(Volt) 

                  
                  

V = voltmeter reading  

(Volt) 

                  
                  

R = resistance of carbon resistors  

(kΩ) 

                  
                  

Rv = resistance of voltmeter  

(kΩ) 

                  
1.  3.80952  10  100 

 

For example: 

E= 8 V 

Voltmeter reading(V) = 3.80952 V 

Resistance of carbon resistors = 10 kΩ 

Resistance of voltmeter=  

=

Conclusion 

A non-ideal voltage measuring device has non-infinite resistance.