Physics!!!!!!!?

Question

Q1)In a dry weather when a driver touches the door before getting out of her car, she sometimes get an electric shock as soon as her foot touches the ground
a:)Explain why this happenes?
b:)Why doesn't it happen in wet weathers?
c:)some ppl fix a piece of fine chain to the car which drags on the road. How does this prevent shock taking place?
d:)Some ppl fix a piece of mental under a car body. Even though it doesn't touch the road, it stops the driver getting an electric shock.How does it do so?

Answer 1

a) Due to the friction between air particles & the body of the car some static electricity is developped in the body.( Familiar example:- a comb , which is used to brush dry hair, gains the ability of attracting small paper strips, immidiately after combing). the driver remaining in the car, some electricity is also stored in his body. As soon as the body is grounded this electricity pass to the earth. So he gets a shock.

b)Moist air is a much better conductor of electricity. So most of the charge generated due to friction gets discharged through the moist air. Sufficient amount of charge is not stored in the driver's body. So he gets no shock or a mild shock.

c) This application is usually seen in petrol tankers. Due to the friction between the oil & the wall of the tanker, huge amount of static electricity is developped in the walls. Which may produce heat & result in a fire. The chain acting as a conductor allows the passage of this chatge to the earth. So sufficient amount of charge never gathers on the surface of the wall. & it diminishes the chance of a fire.

d) Same reason, but this time the metallic plate being situated closer to the earth surface, allows passage of electricity through electric discharge through air. But this arrangement is much risky as the success of it depends on the humidity.

Answer 2

All because of static electricity

a)Due to the abrasion of solid particles suspended in air, static electricity is developed in the car which is insulated from earth by rubber tyres. The car occupants potential is the same as that of the car. So when he touches the ground he's earthed and recieves the shock.

b)In wet weather the dust particles are very less so the extent of static electricity developed is less too. Besides moist air is a much better conductor of electricity. So most of the charge generated due to friction gets discharged through the moist air.Shock becomes undetectable.

c)The chain acts as grounder, so no static electricity is developed at all.

d)The metal piece under the car just touches speed breakers etc, grounding occurs at those time and static charge is drained. Even it it dos ot touch its so close that charge transfer occurs through air that is.

Answer 3

Water is a retardant