How does thunder and lightning work?

Answer 1

Lightning is a discharge of electrical energy that builds up within a storm. The charges develop because a storm causes air to move around which rubs against itself to generate electrical charges. Eventually the charge increases to a point where the electricity can flow through the air. Once an electric discharge starts it provides a better path for more electrical flow than normal air due to ionization which results in a sudden, large and fast discharge (i.e. a lightning bolt).

Negative charges at the bottom of the clouds repel the negative charges on the surface of the earth. This leaves the surface of the earth positive (the electrons on the ground migrate to get further away from the other electrons in the cloud). From there, the negative electrons from the cloud attract the positive electrons on the ground, which pulls electrons from the air. This usually occurs at a high point on the ground.

Answer:
When you have a thunderstorm that forms from convection and differences in temperature across a frontal boundary, you start to get differing charges building up between the cloud base and the ground. When the difference in charge gets great enough between the cloud base and the ground, the air becomes a conductor instead of being an insulator and a negatively charged stepped leader comes down from the cloud base and meets a positively charged return stroke from the ground. When this happens, we see visible lightning and positive charge is carried up into the cloud base, while negative charge is carried down into the ground, essentially it is a transfer of both of the charges involved in the electrical discharge. This lightning strike is called a negative strike because the stepped leader is negatively charged. There is also something called a positive lightning strike, where enough differing charge builds up between the top of the cumulonimbus cloud and the ground and the same transfer of positive and negative charges happens, but the stepped leader from the top of the cloud in this case is positively charged and the return stroke from the ground is negatively charged. Initially the top of the cloud is positively charged, the cloud base is negatively charged, and the ground is positively charged. Positive strikes are possible after several negative strikes between the cloud base and the ground have happened. Lastly, lightning strikes can go out a maximum of 10 miles ahead and behind the storm, so remember just the because it looks like the storm has passed, doesn't mean the threat of lightning doesn't exist. This is a more complete answer to your question. If you have any questions about the concepts that I presented in my answer, feel free to drop me a message on my message board.
When you have a thunderstorm that forms from convection and differences in temperature across a frontal boundary, you start to get differing charges building up between the cloud base and the ground. When the difference in charge gets great enough between the cloud base and the ground, the air becomes a conductor instead of being an insulator and a negatively charged stepped leader comes down from the cloud base and meets a positively charged return stroke from the ground. When this happens, we see visible lightning and positive charge is carried up into the cloud base, while negative charge is carried down into the ground, essentially it is a transfer of both of the charges involved in the electrical discharge. This lightning strike is called a negative strike because the stepped leader is negatively charged. There is also something called a positive lightning strike, where enough differing charge builds up between the top of the cumulonimbus cloud and the ground and the same transfer of positive and negative charges happens, but the stepped leader from the top of the cloud in this case is positively charged and the return stroke from the ground is negatively charged. Initially the top of the cloud is positively charged, the cloud base is negatively charged, and the ground is positively charged. Positive strikes are possible after several negative strikes between the cloud base and the ground have happened. Lastly, lightning strikes can go out a maximum of 10 miles ahead and behind the storm, so remember just the because it looks like the storm has passed, doesn't mean the threat of lightning doesn't exist. This is a more complete answer to your question. If you have any questions about the concepts that I presented in my answer, feel free to drop me a message on my message board.

Answer 2

Thunderstorms often occur at the end of hot, sticky summer days. At this time, warm moist air rises quickly and forms large cumulonimbus clouds. Inside these tall dark clouds, air currents create strong updraughts and water droplets and ice particles rub against each other. As they bang together like this, it causes a build-up of static electricity. Lighter, positive charges gather at the top of the cloud and heavier, negatively-charged pieces of ice and water accumulate at the base. The ground below is also positively charged. Electricity flows between the charges and the difference between them increases. When the differences get big enough, they are neutralised and electricity is released as a flash of lightning.

As the lightning strikes, it heats the air around it. Lightning bolts can heat the air to as much as five times as hot as the surface of the sun - approximately 30,000 °C (54,000 °F). This heat causes the air around to expand explosively, resulting in the loud crash called thunder.