Electric shocks and earthing

Question

If I was to touch a charged object, I may get an electric shock due to the potential difference between myself and the tap and because I am earthed. If I was not earthed, the electric shock would not occur.

When I get out of my car, I can become charged because of the friction between myself and the car seat. Then when I touch the frame of the car, I can get an electric shock because the charge passes from me to the (neutral) car.

However, is there a need for the car to be earthed? Or does the large neutral body of the car act as an 'earthing' system on its own?

If the car can act as an earthing system of its own, why would I not act as an earthing system of my own and get shocked when I touch the tap with insulating socks on (e.g. I'm not actually earthed)?

Edit:

If I was charged myself and touched an earthed object, I would get an electric shock. However, would that be dangerous? The charge will flow from me through the other object as opposed to through me, so there is no damage to me?

Answer 1

How do you know you were earthed when stepping out of the car, did you actually measure the resistance of your shoe soles? Many people happen to wear insulating shoes. In contrast, most cars are earthed because the tires have a resistance of only about 10 MΩ, which is almost zero for static electricity.

In my experience, you will only get the shock when wearing insulating shoes. You will not get the shock when being barefoot outside the car, being effectively earthed.

Your body gets electrically charged by friction with the chair, and you will get a high voltage by the work of removing yourself from the chair, similar to a parallel plate capacitor with an adjustable gap distance between the plates. On insulating shoes, you will preserve your charge and high voltage. But your charge and high voltage are lost immediately when being earthed, for example by being barefoot or by touching the door with a finger.

Answer 2

"The charge will flow from me through the other object as opposed to through me, so there is no damage to me?" If you are charged, the charge will reside all over the surface of your body (essentially because like charges repel). There will be a potential difference between you and the earthed conductor, so that when you touch the conductor with a finger, the charge on parts of your body remote from the finger will travel through your body (quite a good conductor) and out through your finger to the earthed conductor. You could quite possibly be damaged – worst case, heart stopped – by this current through you.