You charge gold leaf, typically within an electroscope, by charging it through induction, as described in the provided reference. This process involves bringing a charged object near the gold leaf assembly without direct contact.
Charging gold leaf, particularly the thin leaf found in devices like gold leaf electroscopes, is a fundamental demonstration of electrostatic principles. While direct contact charging is possible, a common and illustrative method, especially when using an electroscope, is charging by induction.
Charging Gold Leaf by Induction Using an Electroscope
The referenced method details how to charge the gold leaf within an electroscope assembly using the principle of induction. Here's how it works:
- Charge an Insulator: Begin by rubbing an insulator (like a plastic rod or balloon) with another material (like fur or cloth) to give it a static electric charge. Let's assume you charge the insulator negatively.
- Bring Insulator Near Plate: Bring the charged insulator close to the top plate of the electroscope. It is crucial not to let the insulator touch the plate.
- Induce Charge: The charged insulator's electric field influences the charges within the conductive electroscope assembly (the plate, connecting rod, and gold leaf).
- If the insulator is negative, it repels electrons in the electroscope down towards the gold leaf.
- This leaves a net positive charge on the top plate of the electroscope.
- The excess negative charges accumulate on the gold leaf and the connecting rod just above it.
- Gold Leaf Rises: The accumulation of negative charges on the gold leaf and the rod causes them to have the same type of charge. Since like charges repel, the gold leaf is repelled away from the rod, causing it to rise or diverge.
- Remove Insulator: Once the charged insulator is removed, the induced charges redistribute, and the gold leaf will fall back down as the net charge on the assembly returns to zero (assuming the electroscope was initially neutral and no charge was added or removed permanently).
This process temporarily charges the gold leaf assembly, causing the leaf to deflect due to electrostatic repulsion. The reference explicitly states this process "will induce the opposite charge on the plate of electroscope leaving a net charge on the gold leaf, which will rise."
Understanding the Charge on the Gold Leaf
During the induction process described:
- The plate of the electroscope acquires a charge opposite to that of the approaching insulator.
- The gold leaf and the lower part of the rod acquire a charge same as that of the approaching insulator.
It is this net charge on the gold leaf (and the rod it's attached to) that causes the leaf to stand out due to repulsion. The degree to which the leaf rises is indicative of the magnitude of the induced charge.
