Question
Explain with the help of an example that heat is produced by friction.
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Answer
As friction opposes the relative motion between the two surfaces, it produces heat. So, when we rub our hands together vigorously for few minutes, we feel hotness. Similarly when we strike a matchstick against the rough surface, it catches fire.
In machineries also, heat is produced due to friction as the machine parts rub against each other.
In machineries also, heat is produced due to friction as the machine parts rub against each other.
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Activity: To make an electric pen.
Materials required: Potassium iodide salt, water, metal sheet, starch solution, paper napkin, copper wire, battery.
Procedure
1. Take potassium iodide salt solution in a beaker, battery and a metal sheet.
2. Connect the metal sheet to the negative terminal of the battery.
3. Add a few drops of starch solution to it
4. Soak a paper napkin in the potassium iodide solution and place it on the metal sheet.
5. Connect another wire to the positive terminal of the battery. Write with the positive terminal on the paper napkin.
Answers the following questions.
(i) Are you able to write?
(ii) Why is it possible?
Materials required: Potassium iodide salt, water, metal sheet, starch solution, paper napkin, copper wire, battery.
Procedure
1. Take potassium iodide salt solution in a beaker, battery and a metal sheet.
2. Connect the metal sheet to the negative terminal of the battery.
3. Add a few drops of starch solution to it
4. Soak a paper napkin in the potassium iodide solution and place it on the metal sheet.
5. Connect another wire to the positive terminal of the battery. Write with the positive terminal on the paper napkin.
Answers the following questions.
(i) Are you able to write?
(ii) Why is it possible?
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Q.1. What type of eclipse were the students observing?
Q.2. Which Moon phase is required for this eclipse to occur?
Q.3. Why were students told to wear special glasses?
Q.1. What type of eclipse were the students observing?
Q.2. Which Moon phase is required for this eclipse to occur?
Q.3. Why were students told to wear special glasses?
Watson fills a bottle completely with water. The bottle has three same sized plugged holes on Its wall. Watson pulls out the plugs and checks the position of the stream of water coming out.
(i) What does Watson's activity show ?
$\quad$(a) Liquids exert pressure.
$\quad$(b) Liquids contract on cooling.
$\quad$(c) Liquids cannot be compressed.
$\quad$(d) Liquids have no definite shape.
(ii) Liquids exert pressure on the walls of container
$\quad$1. at same depth
$\quad$2. at different depth
$\quad$3. with same strength
$\quad$Which of the following is correct ?
$\quad$(a) Only 1$\quad$(b) Only 3$\quad$(c) Only 2$\quad$(d) Only 1 and 3
(iii) Pressure exerted by liquids at the bottom depends on
$\quad$(a) width of the liquid column
$\quad$(b) shape of the column
$\quad$(c) shape of the container
$\quad$(d) height of the liquid column
(iv) Which of the following does not affect the pressure beneath the surface of a liquid ?
$\quad$(a) Strength of the gravitational field
$\quad$(b) Area of the liquid
$\quad$(c) Density of the liquid
$\quad$(d) Depth of the liquid
→(i) What does Watson's activity show ?
$\quad$(a) Liquids exert pressure.
$\quad$(b) Liquids contract on cooling.
$\quad$(c) Liquids cannot be compressed.
$\quad$(d) Liquids have no definite shape.
(ii) Liquids exert pressure on the walls of container
$\quad$1. at same depth
$\quad$2. at different depth
$\quad$3. with same strength
$\quad$Which of the following is correct ?
$\quad$(a) Only 1$\quad$(b) Only 3$\quad$(c) Only 2$\quad$(d) Only 1 and 3
(iii) Pressure exerted by liquids at the bottom depends on
$\quad$(a) width of the liquid column
$\quad$(b) shape of the column
$\quad$(c) shape of the container
$\quad$(d) height of the liquid column
(iv) Which of the following does not affect the pressure beneath the surface of a liquid ?
$\quad$(a) Strength of the gravitational field
$\quad$(b) Area of the liquid
$\quad$(c) Density of the liquid
$\quad$(d) Depth of the liquid