Answer:
2. The hydrogen atom has quantized energy levels.
Explanation:
The Bohr model of the atom states that the structure of the atom is quantized, that is, that electrons can only orbit the nucleus in specific orbits with a fixed radius. Therefore, the electron cannot be in energy levels that do not correspond to these quantized levels.
Answer:
Acute bronchitis can result from: a virus, for example, a cold or flu virus. a bacterial infection. exposure to substances that irritate the lungs, such as tobacco smoke, dust, fumes, vapors, and air pollution.
Explanation:
Answer: Friction
Explanation:
Friction is a force that opposes the motion of an object on another surface. For example, when a box is pushed along the floor, the floor exerts a frictional force on the box, "resisting" the motion of the box. This force is due to the contact between the molecules of the box and the molecules of the floor, and it is always directed against the direction of motion of the object (so, if the object is moving forward, friction acts backwards).
The magnitude of the friction force is given by:
where 
is the coefficient friction, which is a number that depends on the materials of the two surfaces, and N is the normal reaction.
The answer is Transistor. Its a semiconductor device used to amplify or switch electronic signals and electrical power. It is composed of semiconductor material usually with at least three terminals for connection to an external circuit.
