Investigating Conductors & Insulators | Physics for GCSE/IGCSE - Year 11 PDF Download

Conductors, Insulators & Electrons

• The distinction between conductors and insulators lies in their ability to conduct electricity:
  • Conductors allow charge carriers to move freely, enabling the flow of electricity.
  • Insulators prevent the movement of charge carriers, impeding the flow of electricity.
• The underlying cause for this contrast can be attributed to their internal composition.

Conductors

• A conductor is a substance that permits the easy flow of charge, typically electrons, through it. 
• Examples of conductors include:
  • Silver
  • Copper
  • Aluminium
  • Steel
• Conductors tend to be metals
  
• At the atomic level, conductors consist of positively charged metal ions alongside their outermost electrons, which are delocalized.
  • Consequently, electrons have the freedom to move within the conductor.
• Metals exhibit excellent electrical conductivity due to the following:
  • Electrical current denotes the speed at which charged particles move.
• Therefore, the smoother the movement of electrons, the superior the conductivity of the conductor.
  

Insulators

• Insulators, on the other hand, are materials that do not have free charges readily available and therefore inhibit the flow of electrical charge.
• Common examples of insulators are rubber, plastic, glass, and wood.
• Even though insulators do not conduct electricity well, some non-metals like wood can allow a small amount of charge to pass, particularly in the form of static electricity.
• For instance, when two insulators come into contact, any accumulated charge on their surfaces can be conducted away.

Investigating Electrical Conductors & Insulators

• When exploring electrical conductors and insulators, a Gold-leaf electroscope (GLE) serves as a valuable tool. This device aids in distinguishing between the two types of materials.

• The Gold-leaf Electroscope consists of:
  • A metal plate attached to one end of a metal rod.
  • A very thin leaf of gold foil attached to the other end of the rod.
  • The rod is held by an insulating collar inside a box with glass sides, ensuring visibility and protection of the gold leaf from disturbances.
• When the Gold Leaf Electroscope (GLE) becomes charged, the plate, rod, and gold leaf acquire identical charges, whether positive or negative.
  • As both the rod and leaf possess the same charge, they undergo repulsion, causing the leaf to extend sideways.
  • Upon discharge, when the rod and leaf reach a neutral state, the leaf returns to its hanging position.

Testing Electrical Conductors and Insulators

• Charge the plate of the Gold Leaf Electroscope (GLE) to make the gold leaf stand clear of the rod.
• Touch the plate of the GLE with items being tested:
  • Metals: wire, paperclip, scissor blades
  • Non-metals: paper, fingers, glass, graphite
  • Plastics: plastic ruler, handles of scissors, finger in a plastic bag
  • Comparisons: wet cloth, dry cloth; finger and finger in a plastic bag
• When observing the behavior of a leaf:
  • A leaf falls promptly on a good conductor.
  • If a leaf remains in place, it indicates the object is a poor conductor (good insulator).
  • When a leaf falls slowly, it suggests the material is a poor conductor.
• Alternative Method:
  • An electronic charge detector can be a substitute for the Gold-leaf Electroscope.
• Expected Results
  • Metals are excellent conductors, while non-metals are commonly good insulators.