Static electricity is caused by a build-up of electric charges that are not free to move. This can often result in an electric shock or a spark when the built-up charges eventually move.

For example, if you rub a cloth on a polythene rod, electrons move from the cloth to the rod. This leaves the rod negatively charged and the cloth positively charged.

Remember, opposite charges attract each other. This is called electrostatic attraction, which is a non-contact force. So, the positively charged cloth and the negatively charged polythene rod will pull towards each other. If you had two positively charged cloths, they would push away from each other, known as electrostatic repulsion.

As electric charge builds up on an object, the potential difference between the object and the Earth (which has a potential difference of 0V) increases. If the potential difference becomes large enough, electrons may jump across the gap to the Earth, creating a spark.

Sparks can also leap to an earthed conductor, a material connected to the Earth. This is why it's advisable to avoid tall metal objects like electricity pylons during a thunderstorm. Lightning is an example of a large spark caused by the potential difference between charged storm clouds and the Earth. Electrons from the clouds can jump to metal objects like pylons, resulting in a massive current.

Electric fields are generated by electrically charged objects. The strength of the electric field increases as you get closer to the charged object.

Remember, opposite charges attract each other, which is called electrostatic attraction, a non-contact force. So, if you rub a cloth on a polythene rod, electrons move from the cloth to the rod, making the rod negatively charged and the cloth positively charged. These opposite charges will pull toward each other, while like charges (e.g., two positively charged cloths) will repel each other.