2017 Unit 1 exam - Jsjsjjs PDF

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Melbourne High School

Unit 1 Physics exam 2017

Area of Study 1 – How can thermal effects be explained?

Question 1. (1 mark) What does temperature measure? A. B. C. D.

The total amount of energy in a substance. The energy of the fastest moving particles in a substance. The average potential energy of the particles in a substance. The average kinetic energy of the particles in a substance.

Question 2. (1 mark) Heat is added to a closed system and work is done on the system. What change, if any, will take place in the internal energy of the system?

A. B. C. D.

The internal energy will remain the same. The internal energy will increase. The internal energy will decrease. There is insufficient information to determine the change in the internal energy.

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Melbourne High School

Unit 1 Physics exam 2017

Question 3. (10 marks) 0.1 kg of a substance is heated and its temperature is recorded. The graph of the temperature of the substance versus time is shown in Figure 1 below. Heat energy is added at the rate of 150 J s-1.

Figure 1

a.

State the freezing point of the substance, giving your answer in kelvin. Explain how you can tell this from the graph. __________________________________________________________________________ __________________________________________________________________________ K 2 marks

b. How much heat energy is added to the substance in 2 minutes?

J 2 marks

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c.

Unit 1 Physics exam 2017

Calculate the specific heat capacity of the substance when it is in its liquid state.

J kg-1 K-1

3 marks

d. Calculate the latent heat of vaporisation of the substance. Give your answer in kJ kg-1.

kJ kg-1 3 marks Question 4. (3 marks) Explain how evaporation of a liquid can occur below its boiling point and how evaporation can produce a cooling effect. __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________

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Melbourne High School

Question 5.

Unit 1 Physics exam 2017

(3 marks)

A hot iron frying pan of mass 2.5 kg is placed into a tub that contains 15 litres of water at 24oC. The water and the plate reached thermal equilibrium at 28oC. What was the original temperature of the frying pan, assuming no heat is lost to the surroundings? (Specific heat capacity of iron = 450 J kg-1 K-1; SHC of water = 4200 J kg-1 K-1)

oC

Question 6. (3 marks) Mr Draper adds 70 grams of ice (at 0oC) to his well-earned 300-ml gin and tonic (at 25oC). What is the final temperature of his drink, assuming no heat is transferred to the surroundings? (Latent heat of fusion of water = 3.4 x 10 J kg-1; SHC of water = 4200 J kg-1 K-1. Assume SHC of gin and tonic = SHC of water.)

oC

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Melbourne High School

Unit 1 Physics exam 2017

Question 7. (4 marks) A chilled 250 ml glass of water (mass of 250 grams) is measured to be at a temperature of 4oC when it is removed from the refrigerator and placed on the kitchen bench on a warm day. Sometime later it is measured to be at 23oC, the same temperature as the room. a.

Which of the following statements correctly describes the interaction between the water, the glass and the surrounding air and bench? A. By the time the water molecules reached 23oC, all the substances were no longer at thermal equilibrium. B. By the time the water molecules reached 23oC, only the water had reached thermal equilibrium. C. Thermal energy flowed from water molecules in the glass to the surrounding glass and then to the surrounding air and bench so that all the substances reached thermal equilibrium at 23oC. D. Thermal energy flowed from the surrounding air and bench to the glass and then to the water molecules in the glass so that all the substances reached thermal equilibrium at 23oC. 1 mark

b.

Explain how the zeroth law of thermodynamics explains the interaction between the substances.

__________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2 marks

c.

Describe the changes in the kinetic energy of the water molecules in the glass during this interaction.

__________________________________________________________________________ __________________________________________________________________________ 1 mark

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Question 8. a.

Unit 1 Physics exam 2017

(5 marks)

Explain the difference between convection and conduction in the transfer of heat from one location to another. __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2 marks

b. During the summer, while sitting on the terrace of his Bayside sailing club, Mr Homewood can often feel an onshore sea breeze in the afternoon, which offers cool relief from the heat. In terms of heat transfer, explain why this sea breeze occurs.

__________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 3 marks

END OF AREA OF STUDY 1 7

Melbourne High School

Unit 1 Physics exam 2017

Area of Study 2 – How do electric circuits work? Question 9. (9 marks) A current of 3.2 A is flowing through a toaster. a. How long will it take for 112 C of charge to pass through the toaster?

s 2 marks During this time 26.2 kJ of energy is transformed in the toaster. b. What is the potential difference across the toaster? (Value and SI unit required.)

3 marks Later on, the toaster is operating on a different setting for 2 minutes at a power of 700 W. c. How much energy is dissipated in the toaster: i. in joules?

J

ii. in the unit shown on a domestic electricity bill? (Value and unit required.)

4 marks

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Melbourne High School

Unit 1 Physics exam 2017

Question 10. (5 marks) Doctors Kemp and Shin have plotted the current versus voltage graphs for two different components A and B as shown in Figure 2. Current (mA)

400

200

0

Figure 2 a.

Explain why both components A and B are non-ohmic. __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2 marks

b. What is the resistance of component A at a voltage of 8 V? A. B. C. D.

0.02 Ω 0.05 Ω 20 Ω 50 Ω

1 mark

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Melbourne High School

Unit 1 Physics exam 2017

Dr Kemp thinks that component B is likely to be an LED, whereas Dr Shin thinks it is more likely to be an incandescent light globe. c. Who is correct and why?

__________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2 marks

Question 11. (8 marks)

Figure 3 a.

What is the effective resistance of the combination of three resistors in parallel?

Ω 2 marks

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Melbourne High School

Unit 1 Physics exam 2017

b. What is the total resistance of the whole circuit?

Ω 2 marks c.

What current is flowing through the power supply?

A 2 marks d. What power is being dissipated by the 15 Ω resistor?

W 2 marks

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Melbourne High School

Unit 1 Physics exam 2017

Question 12. (3 marks) A light-dependent resistor (LDR) is connected in series with a 25.7 kΩ resistor and a 15 V power supply. The resistance versus illumination characteristic of the LDR is shown in Figure 4.

Figure 4 The circuit is designed to turn on a switch when the potential difference across the 25.7 kΩ resistor is 10.8 V. What is the illumination on the LDR when the switch operates?

lux

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Melbourne High School

Unit 1 Physics exam 2017

Question 13. (1 mark) Residual current devices (RCDs) are used to reduce the severity of electric shock to a person. They do this by: A. B. C. D.

Preventing any current from flowing through a person. Reducing the voltage applied to the person. Increasing the resistance of the person. Reducing the duration of the shock.

Question 14. (4 marks) Most household wiring circuits should have a circuit breaker and an earth wire. a. What is the purpose of the earth wire? __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2 marks b. What is the purpose of the circuit breaker? __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2 marks

END OF AREA OF STUDY 2

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Melbourne High School

Unit 1 Physics exam 2017

Unit 1 formula and data sheet Thermal physics Specific heat capacity

Q  mcT

Latent heat

Q  mL

First law of thermodynamics

U  Q  W

Wien’s Law

 T  2.898 10 3 m K

Stefan-Boltzmann relationship

P  T4

max

Nuclear and particle physics n

Radioactive decay

 1 N  N0     2

Einstein’s mass-energy equation

E  mc 2

Electricity Q t E V Q V R I RT  R1  R2  … 1 1 1   … RT R1 R2 I

Current Voltage Resistance Resistors in series Resistors in parallel Power

P  I V  I 2 R 

Energy

E  Pt

V2 R

Data speed of light in a vacuum

c = 3.0 × 108 m s-1

charge on an electron

e = -1.6 × 10-19 C

light year

1 ly = 9.46 × 1015 m

atomic mass unit

1 u = 1.66054 × 10-27 kg

electron-volt

1 eV = 1.6 × 10-19 J

Prefixes exa (E)

1018

peta (P)

1015

tera (T)

1012

giga (G) mega (M) kilo (k)

109

milli (m)

10-3

106

micro (µ)

10-6

103

nano (n)

10-9

19

pico (p) femto (f)

10-12

atto (a)

10-18

10-15...