A tightly closed metal lid of a glass bottle can be opened more easily if it is put in hot water for some time. Explain.

While watering a distant plant, a gardener partially closes the exit hole of the pipe by putting his finger on it. Explain why this results in the water stream going to a larger distance.

If a drop of water falls on a very hot iron, it takes long time to evaporate. Explain why?

Figure shows a metal rod PQ resting on the smooth rails AB and positioned between the poles of a permanent magnet. The rails, the rod and the magnetic field are in three mutually perpendicular directions. A galvonometer G connects the rails through a switch K. Length of rod = 15 cm, B = 0.50 T, resistance of the closed loop containing the rod = 9.0mOmega . Assume the field to be uniform. a. Suppose K is open and the rod is moved with a speed of 12cms^(-1) in the direction shown. Give the polarity and magnitude of the induced emf. b. Is there an excess charge built up at the ends of the rods when K is open? What if K is closed? c. With K open and the rod moving uniformly, there is no net force on the electrons in the rod PQ eventhough they do experience magnetic force due to the motion of the rod. Explain. d. What is the retarding force on the rod when K is closed? e. How much power is required (by an external agent) to keep the rod moving at the same speed (=12cms^(-1)) when K is closed? How much power is required when K is open? f. How much power is dissipated as heat in the closed circuit? What is the source of this power? g. What is the induced emf in the moving rod if the magnetic field is parallel to the rails instead of being perpendicular?

Shows a smooth pair of thick metallic rails connected across a battery of emf epsilon having a negligible internal resistance. A wire ab of length l and resistance r can slide smoothly on the rails. The entire system lien in a horizontal plane and is immersed in a uniform vertical magnetic field B. At an instant t, the wire is given a small velocity v towards right. (a) find the current in it at this instant. What is the direction of the current? (b) What is the force acting on the wire at this instant? (c) Show that after some time the wire ab will slide with a constant velocity. Find this velocity.

There is some liquid in a closed bottle. The amount of liquid remains constant as time passes. The vapor in the remaining part.

An ecosystem which can be easily damaged but can recover after some time if damaging effect stops, will be having.

A closed bottle containing water at room temperature is taken to the moon and then the lid is opened. The water will ……………… .

When food is cooked in a vessel by keeping the lid closed, after some time the steam pushes the lid outward. By considering the steam as a thermodynamic system, then in the cooking process .........

Take a glass of water and put some ice cubes inte it. Observe it for some time. What happens? The ice cubes melt and disappear. Why did it happen?