physics test (unit 10-11)viii (1)

7/29/2019 Physics Test (Unit 10-11)VIII (1)

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Theory Section: [Total 17Marks] Class: CIest Unit 10-11

Unique Science AcademyName: ...Paper: PhysicsTime Allowed: 40 Minutes Code 5054 Maximum Marks: 25Date: .

PadBMamIan

D edicated To M y S on M ohamm ad Irtaza Zain [Turn Over]

1 (a) Define specific latent heat of fusion.

..........................................................................................................................................

..........................................................................................................................................

.................................................................................................................................... [1]

(b) (i) A tray of area 0.25 m2, filled with ice to a depth of 12 mm, is removed from arefrigerator.

Calculate the mass of ice on the tray. The density of ice is 920 kg / m3.

mass = ................................................. [2]

(ii) Thermal energy from the Sun is falling on the ice at a rate of 250 W / m2. The iceabsorbs 60 % of this energy.

Calculate the energy absorbed in 1.0 s by the 0.25 m2 area of ice on the tray.

energy = ................................................. [2]

(iii) The ice is at its melting temperature.

Calculate the time taken for all the ice to melt. The specific latent heat of fusion ofice is 3.3 105 J / kg.

time = ................................................. [3]

[Total: 8]

106-A, New Muslim Town, Lahore


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Fig.2.1

Solar panels are positioned on the roof of the house shown in Fig. 2.1. They use thermal2energy from the Sun to provide hot water in an environmentally friendly way.

solar

panels

Cold water flows to the panels at 15 C. During the day, the panels supply 3.8 kg of hot waterat 65 C every hour.

(a) Calculate the average energy that the solar panels deliver to the water in one hour.Specific heat capacity of water = 4200 J / (kg C).

energy = ................................................. [3]

(b) The solar power incident on the roof during this heating period is 170 W / m2. The solarpanels have a total area of 8.0 m2.

Calculate the solar energy incident on the panels in one hour.

solar energy = ................................................. [2]

(c) Calculate the efficiency of the solar panels, stating the equation you use.

efficiency = ................................................. [2]


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(d) Explain why solar energy is called renewable energy.

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..................................................................................................................................... [1]

(e) State one disadvantage of using solar energy.

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[Total: 9]MCQ Section: [Total8Marks]1 Less heat is needed to raise the temperature of 1 kg of copper by 1 C than is needed to raise the

temperature of 1kg of water by 1 C.

Which statement explains this?

A Copper has a higher melting point.

B Copper has a lower specific heat capacity.

C Copper has a smaller specific latent heat.

D Copper is a better conductor of heat.

2 An ice cube, at a temperature of 0 C, has a mass of 10 g. The specific latent heat of fusion of

water is 3 105J/kg.

How much heat energy is needed to convert the ice cube into 10g of water at 0 C?

A 30J B 3000J C 3 104J D 3 106J

3 The graph shows the temperature of a substance as it is heated steadily.

In which part of the graph is the substance boiling?

temperature

time

A

B

C

D


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5

4 A night storage heater contains a large block of material that is heated electrically during thenight. During the day the block cools down, releasing thermal energy into the room.

Which thermal capacity and which night-time temperature increase will cause the most energy tobe stored by the block?

thermal capacityof block

night-timetemperature increase

A large large

B large small

C small large

D small small

After a sheep has its wool cut off, it is harder for it to stay warm when the air temperature falls.

How does the wool help the sheep to stay warm?

A Air can circulate between the wool fibres and heat up the skin by convection.

B Air trapped by the wool fibres reduces heat losses from the skin by convection.

C The wool fibres are curly so it takes longer for heat to be conducted away from the skin.

D The wool fibres conduct heat to the skin from the air outside.

6 Four blocks, made from different materials, are each heated so that they have the same increasein internal energy.

Which block has the smallest thermal capacity?

A

temperature

rise = 3C

B

temperature

rise = 6C

C

temperature

rise = 9 C

D

temperature

rise = 12C


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7 A solid object has a very large thermal capacity.

What does this mean?

A A large amount of energy is needed to make the object become hot.

B A large amount of energy is needed to make the object melt.

C A small amount of energy is needed to make the object become hot.

D A small amount of energy is needed to make the object melt.

8 A heater supplies 80J of energy to a block of metal. The temperature of the block rises by 20 C.

What happens to the block of metal when its temperature falls by 10 C?

A Its internal energy decreases by 40J.

B Its internal energy decreases by 160J.

C Its internal energy increases by 40J.

D Its internal energy increases by 160J.

MCQ Answer Sheet

4 A B C D

3 A B C D

2 A B C D

1 A B C D

8 A B C D

7 A B C D

6 A B C D

5 A B C D

physics test (unit 10-11)viii (1)

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