042 - Electroscope

042 – Electroscope

Instrument for indicating electrical charges  

Charge indicator  

Indicator for electric field strength  

 

Introduction to:  

  • Electrostatic charge  
  • Electrostatic repulsion of charges of the same name  
  • Induction  
  • Transmission of electrical charges  

 

Material:  

  • Canning jar (clean, transparent)  
  • Plastic lid  
  • Wire (approx. 15 cm long) / paper clip  
  • Aluminum foil (a few square centimeters)  
  • PVC Tube/Plastic Ruler/Balloon  
  • Sheep’s wool / wool / a piece of fabric  
  • Glue / Hot Glue  
  • Awl / Scissors  
  • Pliers  
  • Scissors 

Setup:  

  • Poke a hole in the middle of the lid with the awl  
  • Push the wire through the hole  
  • Bend the wire with the help of the pliers: a ring at the top and a hook at the bottom
  • Attach it to the lid with glue  
  • Cut off two strips of several centimeters long and about one centimeter wide from the aluminum foil  
  • Punch holes in the ends of the aluminum strips  
  • Hang the foil strips on the hooks. Make sure they touch each other slightly
  • Close the jar with the lid  

Possible experiments with frictional electricity:  

Experiment 1: 

  • Rub the PVC pipe (rubbing rod) vigorously with the sheep’s wool 
  • Brush along the wire ring at the top of the electroscope with the rubbing rod

 Observation: 

  • The two aluminum strips spread from each other laterally (deflection) 
  • If the rubbing rod is removed, the rash remains  
  • Only when you touch the wire ring with your fingers does the rash go down  

Explication: 

  • The PVC rod is positively charged by rubbing with the sheep’s wool, the sheep’s wool negatively
  • The electrical charge on the friction rod partially jumps to the wire ring and is distributed on the conductive parts of the electroscope.  
  • The two aluminum strips are loaded with the same name and repel each other 
  • If you touch the finger with the wire ring, the charge flows off again and the deflection subsides

Experiment 2:  

  • Rub the PVC pipe (rubbing rod) vigorously with the sheep’s wool
  • Approximate the rubbing rod to the wire ring at the top of the electroscope  

Observation:  

  • The two aluminum strips spread from each other laterally (deflection)
  • If you remove the rubbing rod, the deflection goes down  

Explication: 

  • The electric charge on the friction rod influences a charge of the same name at the ends of the two aluminum strips, so that they repel each other  

Note:  

  • In practice, a small deflection often remains because charges jump through the air to the wire ring 

Tips:  

  • Experiments with frictional electricity often fail in humid air or wet hands, as the water acts as a lubricant and hinders friction
  • The balloon can also be electrically charged by rubbing it on the hair 
  • You can also charge your shoe soles by rubbing them on a plastic carpet