Problem: You couldnt survive without your skin. It has many important functions. The main function of the skin is controlling what enters and leaves the body. It prevents the loss of too much water from the body. It also prevents bacteria and other microorganisms from entering the body. The skin helps maintain a constant body temperature. It keeps the body cool in two ways. Sweat from sweat glands in the skin evaporates to cool the body. Blood vessels in the skin dilate, or widen. This action increases blood flow to the body surface. This allows more heat to reach the surface. The heat is then able to radiate off the body. The opposite happens to retain body heat. Blood vessels in the skin constrict, or narrow. This decreases blood flow to the body surface. This reduces the amount of heat that reaches the surface. When this happens, less heat can be lost to the air.

Question: "What are two ways in which the body cools down?"

Answer: "Sweating and constricting blood vessels"
Answer: no

Problem: Rolfe put down the little dog he had been holding, and went out into the hall. The dog accompanied him, frisking about him in friendly fashion. Rolfe first examined the bedroom that he had seen Inspector Chippenfield enter. It was a small room, containing a double bed. It was prettily furnished in white, with white curtains, and toilet-table articles in ivory to match. A glance round the room convinced Rolfe that it was impossible for a man to secrete himself in it. The door of the wardrobe had been flung open by the inspector, and the dresses and other articles of feminine apparel it contained flung out on the floor. There was no other hiding-place possible, except beneath the bed, and the ruthless hand of the inspector had torn off the white muslin bed hangings, revealing emptiness underneath. Rolfe went out into the hall again, and entered the room next the bedroom. This apartment was apparently used as a dining-room, for it contained a large table, a few chairs, a small sideboard, a spirit-stand, a case of books and ornaments, and two small oak presses. Plainly, there was no place in it where a man could hide himself. The next room was the bathroom, which was also empty. Opposite the bathroom was a small bedroom, very barely furnished, offering no possibility of concealment. Then the passage opened into a large roomy kitchen, the full width of the rooms on both sides of the hall, and the kitchen completed the flat.

Question: "Why did Rolfe stop his search in the first room?"

Answer: "Because all hiding places were empty"
Answer: yes

Problem: You may wonder if there are other examples of static discharge. The answer is yes. Lightning is a form of static discharge. It is much more dramatic than what happens between you and the door knocker, but it is the same principle. You can see how it occurs in the following diagram and animation. You have no doubt seen lightning in a rainstorm. What does lighting have to do with static electricity? As it turns out, everything! During a rainstorm, clouds develop regions of different charges. This happens due to the movement of air molecules, water drops, and ice particles. The negative charges are concentrated at the base of the clouds. The positive charges are concentrated at the top. The negative charges repel electrons on the ground below. The ground then becomes positively charged. Over time the differences increase. Eventually the electrons are discharged. This is what we see as lightning. You can watch an awesome slow-motion lightning strike below.

Question: "What happens to electrons to make them turn into lightning?"

Answer: "Electron becomes neutrally charged"
Answer:
no