1. On a winter morning, a marble tile would feel colder than a wooden tile because the marble tile
(a) conducts heat more effectively than the wooden tile.
(b) Whereas the hardwood tile is not polished, more heat is reflected by
(c) than by the wooden tile.In comparison to the hardwood tile,
(d) is a poor heat conductor.
1. On a winter morning, a marble tile would feel colder than a wooden tile because the marble tile
(a) conducts heat more effectively than the wooden tile.
(b) Whereas the hardwood tile is not polished, more heat is reflected by
(c) than by the wooden tile.In comparison to the hardwood tile,
(d) is a poor heat conductor.
Solution:
The proper response is choice (a).
(a) conducts heat more effectively than the wooden tile.
Explanation:
Comparatively speaking, "marble tile" is a better heat conductor than "wooden tile." A marble tile will enable heat to move through itself readily, keeping it chilly on a winter morning since marble is a better heat conductor than wood.
2. On a chilly winter night, a beggar covered himself with many layers of newspaper. This assisted him in maintaining his body temperature because
(a) heat is generated by friction between the newspaper layers.
(b) The air that is confined between the newspaper layers is a poor heat conductor.
(c) Heat can be conducted through newspaper.
(d) The temperature of the newspaper is higher than the ambient temperature.
2. On a chilly winter night, a beggar covered himself with many layers of newspaper. This assisted him in maintaining his body temperature because
(a) heat is generated by friction between the newspaper layers.
(b) The air that is confined between the newspaper layers is a poor heat conductor.
(c) Heat can be conducted through newspaper.
(d) The temperature of the newspaper is higher than the ambient temperature.
Solution:
The correct response is (b), as air trapped between the newspaper layers is a poor heat conductor.
He will be able to stay warm since his body's heat won't escape into the environment.
The newspaper's layers are holding onto air, which is a poor heat conductor. Thus, this aids in keeping him warm.
3. Boojho and Paheli took their temperatures. Boojho measured 37°C, while Paheli measured 98.6 °F. Which of the subsequent claims is accurate?
(a) Paheli's body temperature is greater than Boojho's.
(b) Paheli's body temperature is lower than Boojho's.
(c) Their body temperatures are both normal.
(d) Both people have fevers.
3. Boojho and Paheli took their temperatures. Boojho measured 37°C, while Paheli measured 98.6 °F. Which of the subsequent claims is accurate?
(a) Paheli's body temperature is greater than Boojho's.
(b) Paheli's body temperature is lower than Boojho's.
(c) Their body temperatures are both normal.
(d) Both people have fevers.
Solution:
The response is (c) Their body temperatures are both normal.
There are two temperature measuring scales: degree Celsius and degree Fahrenheit. The average human body temperature is 37°C, or 98.6°F. They both have normal body temperatures as a result.
Fahrenheit and Celsius scales are the two main types of scales used to measure temperature in general.
The average temperature in Celsius and Fahrenheit is 37 degrees Celsius and 98.6 degrees F, respectively.
So, it is normal that they both have the same temperature.
The conversion equation c=5/9 can be used to further confirm this (F-32)
The conversion formula, where C stands for temperature in Celsius and F for temperature in Fahrenheit, can also be used to confirm this.
4. Figure 4.1 depicts the three thermometers that Boojho has. He's interested in comparing the temperatures of his body with boiling water. What thermometer(s) ought he to select?
(A) A thermometer that may be used to gauge body temperature, boiling water temperature, or both.
(b) Thermometer I in for determining both temperatures.
(c) A thermometer (ii) to gauge both of their temperatures.
(d) A thermometer (iii) to gauge both of their temperatures.
4. Figure 4.1 depicts the three thermometers that Boojho has. He's interested in comparing the temperatures of his body with boiling water. What thermometer(s) ought he to select?
(A) A thermometer that may be used to gauge body temperature, boiling water temperature, or both.
(b) Thermometer I in for determining both temperatures.
(c) A thermometer (ii) to gauge both of their temperatures.
(d) A thermometer (iii) to gauge both of their temperatures.
Solution:
The clinical thermometers shown in images (I) and (III) are solely used to assess body temperature.
Thermometer I or (ii) for measuring body temperature and (ii) for measuring boiling water temperature is choice (a) for the right response.Pictures 1 and 3 show clinical thermometers for taking body temperatures, whereas image 2 shows a lab thermometer for taking room temperatures.
5. Figure 4.2 illustrates four different ways to use a laboratory thermometer to estimate the temperature of the ice in a beaker (a, b, c and d). Which one of these best exemplifies the ideal configuration for precise temperature measurement?
5. Figure 4.2 illustrates four different ways to use a laboratory thermometer to estimate the temperature of the ice in a beaker (a, b, c and d). Which one of these best exemplifies the ideal configuration for precise temperature measurement?
Solution:
Fig(a) is the best choice.
As indicated in the image below, there are four different ways to measure the temperature of ice in a beaker, and only one of them is the proper way to measure temperature accurately. Explain why.
Fig(a) is the best choice. The thermometer is erect (not inclined), the bulb is entirely encircled by liquid, and it is not contacting any surface.
fib(b) - Bulb is in contact with surface ( which is wrong)
Fig. (c): Liquid is not entirely encircling the bulb ( which is wrong)
The thermometer is inclined in Fig ( which is wrong)
6. A pupil viewing a doctor's thermometer is seen in Fig. 4.3 (a–d). Which of the figures represents the proper way to measure temperature?
6. A pupil viewing a doctor's thermometer is seen in Fig. 4.3 (a–d). Which of the figures represents the proper way to measure temperature?
Solution:
The correct option is (a)
The thermometer should be held horizontally directly in front of your eyes as you check the temperature reading. Option A illustrates how to read the thermometer correctly. As a glass thermometer measures using lines, it might be a bit challenging to read. See where the mercury line of the thermometer finishes by holding it up to your eyes. Your body's temperature will be that. Keep the thermometer squarely in front of your eyes and examine the temperature reading for the best results. When the thermometer is horizontal, the cohesion force between the glass and the mercury provides an accurate reading.
7. The readings on four separate thermometers are displayed in Figure 4.4. (a-d). Which reading do you think best represents the natural temperature of the human body?
7. The readings on four separate thermometers are displayed in Figure 4.4. (a-d). Which reading do you think best represents the natural temperature of the human body?
Solution:
The measurement in Figure C indicates that the human body temperature is 37°C.
As a result, choice (C) is accurate. The thermometer should be held horizontally directly in front of your eyes as you check the temperature reading. The clinical thermometer is exclusively intended for use in measuring body temperature in humans. The average body temperature of a person is between 35 and 42 degrees Celsius. This thermometer's range is 35°C to 42°C for that reason.
8. Ice blocks are frequently covered with jute bags by store owners. Tell us why.
8. Ice blocks are frequently covered with jute bags by store owners. Tell us why.
Solution:
As materials like jute bags, sawdust and newspapers work as insulators and cannot enable heat to leave or enter through them, store owners who sell ice blocks typically cover them with them.
Shop owners that sell ice blocks cover them with jute bags because, as we all know, when the ice is left uncovered, heat will transfer from the surrounding air to the ice blocks, causing them to melt. Jute is an insulator, meaning that heat cannot travel through it. As a result, the ice doesn't melt.
9. As illustrated in Figure 4.5, a laboratory thermometer A is maintained 7 cm to the side of the flame, and a comparable thermometer B is kept 7 cm above the flame of a candle. Which thermometer—A or B—will indicate a bigger increase in temperature? Reason for your response.
9. As illustrated in Figure 4.5, a laboratory thermometer A is maintained 7 cm to the side of the flame, and a comparable thermometer B is kept 7 cm above the flame of a candle. Which thermometer—A or B—will indicate a bigger increase in temperature? Reason for your response.
Solution:
The answer is picture b) because a candle that is burning due to convection causes hot air to rise.
As the flame and thermometer are not in touch, heat cannot transfer through conduction. It will thus move either by radiation or convection.
As a result of the air being heated near the candle and hot air rising, heat can only move through convection at the higher section of the candle at this time.
Any direction may be involved in the transport of heat by radiation.
When the thermometer is maintained away from the flame on the side, only radiation may transfer heat to the thermometer's bulb. Due to the thermometer's distance from the flame, both convection and radiation can transfer heat to the thermometer's bulb. As a result, the thermometer's bulb will get more heat, causing it to increase the temperature will be high.
10. Paheli covered the jar holding her soup with a woollen cloth to keep it warm. Can she use the same technique to keep a glass of ice-cold beverage chilled? Reason for your response.
10. Paheli covered the jar holding her soup with a woollen cloth to keep it warm. Can she use the same technique to keep a glass of ice-cold beverage chilled? Reason for your response.
Solution:
Since wool is an insulator that prevents heat from escaping or entering, the woollen fabric may be used to keep a glass of cold beverage cool.
Wool is an insulator because it conducts heat poorly. Hence, Paheli's usage of a woollen fabric to wrap the cold drink bottle will keep the beverage cold because there won't be any heat transmission from the outside surroundings.
11. When the bulb of a mercury thermometer makes contact with a heated item, the mercury level in the device increases. What is the cause of this increase in mercury levels?
11. When the bulb of a mercury thermometer makes contact with a heated item, the mercury level in the device increases. What is the cause of this increase in mercury levels?
Solution:
As mercury expands when heated, its level rises in the capillary when it comes into contact with a hot object.
When the mercury thermometer bulb comes into touch with a hot object, heat is transferred to the bulb because of the difference in temperatures between them. This causes the mercury to heat up. As a result, the capillary tube's mercury level rises.
It uniformly expands when heated.
It has a low specific heat capacity.
Its low freezing point is -39 degrees Celsius, while its maximum boiling point is 357 degrees Celsius.
It effectively conducts heat.
It doesn't stick to the inside of the glass tube.
It is easily observable since it is opaque and sparkling.
It may be bought in its most basic state.
12. As seen in Figure 4.6, a metal loop is heated at point O.
(i) What way would the loop's heat flow?
(ii) If points O, P, Q, and R are equally spaced apart from one another, in what sequence do the pins at points P, Q, and R fastened with the aid of wax fall?
12. As seen in Figure 4.6, a metal loop is heated at point O.
(i) What way would the loop's heat flow?
(ii) If points O, P, Q, and R are equally spaced apart from one another, in what sequence do the pins at points P, Q, and R fastened with the aid of wax fall?
Solution:
according to the stated circumstance.
I The heat will go from O to P and from O to R.
ii) The pin at Q will fail after the pins at R and P fail simultaneously.
The temperature at point O rises as the loop is heated. Due to the metal nature of the loop, heat will travel from O to R and O to P, which are both warmer than Q. The heat is transferred via. In other words, heat will go in both the O to P and O to R directions.
13. Pins P and Q are wax-fixed to a metal loop and an iron rod in the combinations A and B seen in Figure 4.7. Which makes it more probable that both pins will fall at separate times? Explain.
13. Pins P and Q are wax-fixed to a metal loop and an iron rod in the combinations A and B seen in Figure 4.7. Which makes it more probable that both pins will fall at separate times? Explain.
Solution:
Because pin P will be the first to feel the heat in situation 'B,' the pin P will fall before the pin Q. In scenario "A," heat spreads in both directions, causing pins P and Q to fall at the same time. The heat travels in both directions in example "A" Hence, P and Q will stop functioning at the same time as the pins. The pin P won't succeed in scenario 'B' before the pin Q. The cause of such heat will be discovered at pin P initially.
14. A tiny quantity of curd is added to heated milk to help it set. If the mixture's temperature maintains roughly between 35°C and 40°C, the curd's bacteria aid in setting. The establishment of curd becomes challenging in locations when the room temperature remains significantly below the range. Provide an idea of how to set curd in that circumstance.
14. A tiny quantity of curd is added to heated milk to help it set. If the mixture's temperature maintains roughly between 35°C and 40°C, the curd's bacteria aid in setting. The establishment of curd becomes challenging in locations when the room temperature remains significantly below the range. Provide an idea of how to set curd in that circumstance.
Solution:
To maintain the proper temperature, wool or another insulator should be placed on top of containers holding curd. Curd may also be made in an area that is cooler than optimum by keeping the container close to the gas stove.
(I) The container can be covered with wool or any other material that is a poor conductor of heat in order to keep the mixture at the proper temperature. The combination can also be maintained in a heat-resistant container as an alternative.
(ii) When cooking, the container can be left in the sunlight or next to the gas burner.
15. You may have observed that the clinical thermometer receives a few quick jerks before use. Why is it the case?
15. You may have observed that the clinical thermometer receives a few quick jerks before use. Why is it the case?
Solution:
Before using the thermometer, apply jerks to allow the mercury level to flow into the bulb below the typical temperature in order to obtain an accurate reading.
The mercury level will drop below normal temperature as a result of the shock, which will enable mercury to flow into the bulb above the kink.
Clinical Thermometer:
The medical industry use clinical thermometers. It was developed to gauge a person's body temperature.
The bulb at the end of the long, thin glass tube is filled with mercury.
To achieve an accurate reading, the thermometer is given a few quick jerks before usage, which causes the mercury level to flow into the bulb at a cooler temperature than usual.
When the mercury level pours into the bulb at a lower temperature than usual, a few quick jerks are applied to the clinical thermometer to ensure appropriate reading.
16. Why is it advised against reading a thermometer when holding it by its bulb?
16. Why is it advised against reading a thermometer when holding it by its bulb?
Solution:
The thermometer should not be held by the bulb while being read since the mercury level rises as a result of our body warmth and affects the reading. Always read the mercury level on a thermometer while holding it at its upper end. The mercury will expand by our body temperature if we hold the thermometer by its bulb while reading it.
Thermometer:
A thermometer is a device that uses the physical characteristics of various substances to determine temperature.
It has two crucial parts: the first one senses a temperature change, and the second one transmits the temperature change.
It is advised to avoid touching the thermometer bulb while taking a reading because one's body temperature may impact the result.
The mercury in the bulb may expand as a result of body heat, giving an inaccurate reading.
Thus, we shouldn't hold the thermometer's bulb in our hands.
17. There are tents of two colours at a campsite—one is made of black cloth, the other of white. Which one do you think you'll favour for a summer afternoon nap? Provide an explanation of your decision. Do you want to use the same tent in the winter?
17. There are tents of two colours at a campsite—one is made of black cloth, the other of white. Which one do you think you'll favour for a summer afternoon nap? Provide an explanation of your decision. Do you want to use the same tent in the winter?
Solution:
A tent made of white cloth will be a better alternative than a tent made of black fabric on a hot summer afternoon.
Black is a good heat absorber but a poor heat reflector (sun light). White, on the other hand, is a great heat reflector and a poor absorber (sun light).Hence, a tent made of white fabric will be favoured on a hot summer afternoon and a tent made of black fabric would be preferred on a chilly winter day.
18. When constructing a home near the ocean, which direction should the windows preferably face and why?
18. When constructing a home near the ocean, which direction should the windows preferably face and why?
Solution:
Houses close to the coast should, wherever feasible, have windows facing the water since the breeze from the ocean will keep the interiors cool during the day.
As the breeze from the sea is flowing towards the land, particularly during the afternoon due to the comparable temperature of the land, windows should preferably face the beach when building a house near the coast since this would help keep the house cool throughout the day.
19. Look at the illustration in Figure 4.8. A pan with a broad base is heating water to boiling.
P or T, which posture feels warmer?
19. Look at the illustration in Figure 4.8. A pan with a broad base is heating water to boiling.
P or T, which posture feels warmer?
Solution:
To indicate the direction of heat transfer to the hand, fill in the boxes P and T.
Due to the hot air ascending, Position "P" will feel warmer. Convection, P Radiation T Due to the heated, rising air around the boiling water and the convection mechanism that results, heat is transferred to P. Yet, there is no convection and the air does not feel as hot as it does at the top on the sides, like at T.
Location "P" will feel warmer as a result of hot air ascending.
P Convection
Radiation T
20. In the instance of A, the length of the wire PQ is equal to the diameter of the semicircle that the wire CDE forms in the case of B. As seen in Figure 4.9, wax is used to secure one pin to each wire. Who will lose a pin first? Explain.
20. In the instance of A, the length of the wire PQ is equal to the diameter of the semicircle that the wire CDE forms in the case of B. As seen in Figure 4.9, wax is used to secure one pin to each wire. Who will lose a pin first? Explain.
Solution:
As heat reacts to the pin on the wire in example A before it reacts to the pin in case B, the pin on the wire in case A will fall first.
The length CDE is bigger than CE since it is the semicircle's perimeter because the length PQ = CE. As a result, the heat takes longer to reach point C than point P.As a result, since heat will reach pin in figure "A" before pin in figure "B," pin in figure "A" will fall first.
