• An insulated plug into • An earthed container with a glass front. • A gold leaf that is attached near the base of the metal rod.
The gold leaf electroscope detects charge in the following manner
• When a charged object is brought near an electroscope, opposite charge is attracted up to the cap of the electroscope. 7
• Charge of the same type as the object being studied is repelled down to the base of the metal rod and the gold leaf.
• Due to the repulsion of the like charges on the base of the metal rod and the gold leaf, the leaf diverges.
• This same phenomenon occurs regardless of the whether charge on the object being studied is positive or negative.
Fig 15.11: Demonstration of detecting charge using a gold leaf electroscope Charging an electroscope by induction
• Bring a charged insulator close to the metal cap, thus inducing a charge on the cap. • Earth the cap by touching it.This causes the charge to flow to the earth rather than the base of the metal rod and the gold leaf.This causes the leaf to collapse.
• Remove the earth and then remove the charged insulator.The electroscope now has an abundance of the opposite type of charge to the charged insulator.
• A polythene rod will induce a positive charge on the electroscope. • A Perspex rod will induce a negative charge.
BENJAMIN FRANKLIN, 1706–90 (AMERICAN)
He discovered lightning is a form of electricity. He was also one of
the ‘founding fathers’ of the United States of America and his portrait is on the $100 bill.
Fig 15.12: Demonstration of charging a gold leaf electroscope by induction
7 In reality it is only the electrons that can move; they are either drawn up by positive or repelled down by negative. However, it is acceptable to refer to ‘charge’ moving without reference to the physical particles carrying the charge.
