Grounding, also called earthing, means connecting an object to Earth through a conducting path so that electrons can move between the object and Earth. In IB Physics D.2, this explains how objects are neutralized or charged by electrostatic induction. This content applies to both SL and HL.
How Grounding Works
Earth is an extremely large conductor that can accept or supply electrons without developing a significant net charge. When a conductor is grounded, electrons move until there is no longer a potential difference driving further charge transfer.
| Situation | Electron movement and result |
|---|---|
| Negatively charged conductor is grounded | Excess electrons flow from the conductor into Earth, neutralizing the conductor. |
| Positively charged conductor is grounded | Electrons flow from Earth into the conductor, neutralizing it. |
| Negative rod is near a grounded neutral conductor | Electrons in the conductor are repelled into Earth, leaving the conductor positively charged. |
| Positive rod is near a grounded neutral conductor | Electrons are attracted from Earth into the conductor, leaving it negatively charged. |
In metals, the mobile charge carriers are electrons. Positive charges do not normally travel through the conductor; a positively charged conductor has a deficiency of electrons.
For charging by induction, the order is essential:
- Bring a charged object close to the neutral conductor without touching it.
- Ground the conductor, allowing electrons to enter or leave.
- Remove the grounding connection while the charged object remains nearby.
- Remove the charged object.
The conductor is left with a net charge opposite to that of the nearby object. Charge is conserved because the transferred electrons came from or moved into Earth.
A common misconception is that grounding “destroys” charge. It does not; it transfers electrons between the object and Earth.
Exam Technique
For an Explain question, state the direction of electron movement, identify whether electrons are attracted or repelled, and give the resulting charge. In an induction sequence, explicitly state that the ground must be removed before the inducing object.