Photo AI
Lightning is a naturally occurring electrostatic discharge - Leaving Cert Physics - Question b - 2021
Question b
Lightning is a naturally occurring electrostatic discharge. It is caused by an imbalance between two electrically charged regions, usually a cloud and the ground. (... show full transcript
Worked Solution & Example Answer:Lightning is a naturally occurring electrostatic discharge - Leaving Cert Physics - Question b - 2021
Step 1
As charge builds up on a cloud, the cloud induces a charge on objects on Earth. Explain how objects can be charged by induction.
Answer
When a charged cloud accumulates a negative charge, it induces positive charges in a neutral object, such as a tree or a person on the ground. For example, when a charged cloud A approaches a neutral object B, the negative charges in object B are repelled by the cloud's electric field, causing the positive charges to move towards the side closest to the cloud. This leaves the far side of the object negatively charged. If the object is then grounded, the negative charges can escape, resulting in a positively charged object. A labelled diagram can illustrate this process, showing cloud A, object B, and the movement of charges.
Step 2
Calculate the power generated when lightning discharges.
Answer
The power generated can be calculated using the formula:
where:
- E is the energy in joules (0.9 GJ = 0.9 \times 10^9 J)
- t is the time in seconds (0.3 ms = 0.3 \times 10^{-3} s)
Thus, substituting the values:
.
Therefore, the power generated is approximately 3 TW.
Step 3
Draw a diagram to show the distribution of charge on a pear shaped conductor.
Answer
A diagram should depict a pear-shaped conductor illustrating that the charge density is higher at the pointy end of the conductor due to the shape. The charges should be shown to concentrate more at the narrower tip while tapering off towards the broader part of the conductor.
Step 4
Describe an experiment to show that static charge accumulates on the outside of a metal object.
Answer
One can perform a simple experiment using a hollow conductor, such as a conductive sphere. Firstly, charge the conductor using a charged object, like a glass rod. Then, place a proof plane (a small metal leaf) near the surface of the charged conductor and connect it to a galvanometer (GLE). When the proof plane touches the exterior of the charged conductor, it will gather some charge and show a deflection on the GLE. If the proof plane is held inside the hollow conductor, very little or no deflection will be seen, demonstrating that static charge accumulates on the outside of the metal object.