Current Measuring Device has Finite Non-zero Resistance

Materials Required

  • Cell
  • Key
  • Rheostat
  • Ammeter
  • Digital multimeter (DMM)  

 

The Procedure

 Real Lab Procedure

  • Make a circuit using a cell, key, rheostat, ammeter, and a digital multimeter (DMM).  
  • Connect the positive terminal of the battery to the ammeter.
  • Connect the lower end of a rheostat to the negative terminal of the ammeter.
  • Connect the upper end of the rheostat to the key.
  • Connect the key to the negative terminal of the battery.
  • Connect a multimeter across the ammeter.
  • Switch on the cell. 
  • Close the key and then adjust the rheostat so that a current of the order of 1 A flows through the ammeter.   
  • Observe the voltage drop (V) across the ammeter with the voltmeter DMM in dc mV range.   
  • Record your observations. 
  • Find the resistance of the ammeter by the ratio of the voltage drop V to the ammeter reading, [R = V/ I] ohm.   
  • Repeat the procedure for different ammeter readings and calculate the mean value of the resistance.  

             

 

Simulator Procedure

  • Click on the check box to show/hide the circuit diagram and connect the circuit.
  • Drag and drop the wire from the +ve end of the cell to +ve end of Ammeter.       
  • Drag and drop the wire from the –ve end of the cell to the key. 
  • Drag and drop the wire from the key to the upper end of rheostat. 
  • Drag and drop the wire from the –ve end of the ammeter to the lower end of the rheostat.
  • Drag and drop the wire from the +ve end of the ammeter to the +ve end of the digital multimeter. 
  • Drag and drop the wire from the -ve end of the ammeter to the -ve end of the digital multimeter. 
  • Drag and drop the key into the key holder.  
  • Move the rheostat slider by using the slider. 
  • Note reading in ammeter and Digital multimeter. 
  • Click on the Show Result button to view the results. 
  • Repeat the above procedure by moving the slider.
  • Click on the Next button. 
  • Observe the observation table. 
  • Click on the next button after referring to the observation table. 
  • Repeat the above procedure using another ammeter. 
  • Click on the Inference button to show the observation. 
  • Click on the reset button to redo the experiment

Observations

Sl.no  Current(A)  Multimeter reading (mV)  Resistance (Ohm)