Heat

We know that marble is the conductor of heat and cold so during winter morning it allows the cold to pass through it due to which it feels cold when touched while wood being an insulator (bad conductor of heat and cold) does not become cold when touched during winter morning.

This is because of the fact that Newspaper belongs to the category of insulator, so it does not allow the heat and cold to flow through it.

As a result, beggar wrap himself around with the newspaper so that heat from his body does no go out and also the cold from outside does not enter into his body.

Since 1°C = 33.8°F and we know that our normal body temperature is 37°C so when we multiply 37°C by 33.8°F we get

37 × 33.8= 98.6 so we get to know that 37°C is equivalent to 98.6°F so the option is correct.

For measuring body temperature we use clinical thermometer (fig i)since its range is 35 to 42 degree Celsius which can be use to get the temperature of fever body of human being then it was replaced by digital thermometer (fig iii )since it was error free and also there was no risk of mercury as it is toxic and can even lead to death.

Fig ii is the clinical thermometer which is used to measure the temperature of bodies having a higher temperature which is out of range of a normal thermometer.

We know that the clinical thermometer should be held straight without any bend and should be kept inside that substance completely so that bulb can take the right measurements so this criterion is satisfied by the fig (a) and (b).

But the clinical thermometer should not touch the surface but we see that in fig (b), thermometer touches the bottom surface which is not correct as it leads to faulty measurement value so fig a is the correct choice.

For getting the accurate reading without any error, mercury level inside thermometer should be in the same line with the eye. We see that fig a satisfies this criteria so option a is correct.

First we know that the normal human body temperature is 37°C OR 98.6°F.

In the above figure, we notice that it is in Celsius scale since the highest temperature possible is 42 degree. So it is surely Celsius scale and we know that in Celsius it will be 37 degrees which are depicted in figure C.

Shopkeepers selling ice blocks have to prevent the ice blocks from melting so they cover ice blocks with the jute sacks or any other such material since Jute sack is an insulator (Bad conductor of heat- does not allow heat to pass through it), so the jute sack prevents the ice from melting as

a) it does not allow the heat from outside to pass through it and enter into ice.

b) Also, jute sack prevents the cold to pass through it.

Thermometer B will show a greater rise in temperature.

Air near candle gets heated up and rises by convection so thermometer B will receive more heat than Thermometer A.

Yes, She can use the same woolen cloth to keep the cold drink cool as Woolen is an insulator and thus is a bad conductor of heat so when it is wrapped around cold drink, it does not allow the heat from outside to enter into the glass and in this way it keeps the drink cool.

Mercury is sensitive to heat and belongs to the category of substances that expands upon heating as a result when mercury comes in contact with the hot object, it expands due to which its volume increases and as a result, we see the rise in the level of mercury.

(i) Heat flows in solid in all direction, with the same speed so heat will flow from O to P and also from O to R.

(ii) First heat travels to R and P so the pin R and P will fall first then the heat goes to point Q so now the pin Q will fall down.

In fig B, pins are likely to fall apart at a different time while in fig A, pins will nearly fall at the same time.

Heat travels in the solid by conduction, in fig B we see that point P is closer to heat and then point Q, so the heat that travels in the rod will reach P first and after some time it will reach point Q.

While in fig A, heat will reach the points P and Q simultaneously since both points are located at the same distance from burning candle.

In order to keep the temperature from 35°C to 40°C, curd can be surrounded by the insulator such as jute, woolen material etc so that heat cannot escape outside and, in this way, temperature does not drop below 35°C.

Also, One can place the curd directly in sunlight in order to maintain the temperature in the range of 35°C to 40°C.

We know that clinical thermometer is used to measure our body temperature so it is given jerk before use so that if the mercury level is above 35°C (normal body temperature) then the jerk will lower down the mercury level until it gets below 35°C so that it can be used again.

Bulb in the thermometer contains mercury so when we hold the thermometer by its bulb then our body temperature which is normally 37°C is enough to expand mercury (Yes mercury expands on heating although here we are not heating but it is very sensitive to temperature) as a result the shape of the thermometer gets distorted and we get faulty reading.

During Summer time, I will prefer the tent with the white fabric since the light colors are the bad absorber of heat so the white color will reflect back all the sunlight.

In Winter I will go with black fabric tent as black is the good absorber of heat so it will absorb all the rays falling over it and will help to keep the tent warm during winter.

Windows in the house should face the coastal areas since during day time when the temperature is relatively high as compared to night then land gets heated up due to which air above the land gets hot while the air above the sea is cool so it travels from sea to land and in order to complete the cycle air flows from land to sea thus leading to the phenomena of sea breeze, as a result, the person sitting near the window will feel cool air even during hot day.

The figure underneath demonstrates land breeze during day time.

(i) P will feel warmer as point P will be heated by both convection ( hot air rising up) while point T will be heated by radiation.

(ii) P - Convection

T – Radiation

Pin on the wire in fig A will fall first since we know that heat travels by conduction in solid and the distance (which is PQ) is less in fig A as compared to fig B (which is CE) so heat reaches pin in fig A faster and makes it fall down.