Physic LCHL Mock Exams 2020 - Physics (Higher Level) - Time: 3 hrs Name:_ - Ashfield College

Physic LCHL Mock Exams 2020

 Physics (Higher Level)

 Thursday 12th March 2020

Answer ANY 3 questions from Section A and

 ANY 5 questions from Section B

 Time: 3 hrs

 Name:____________________________

Section A Answer ANY THREE Questions from this Section 120 Marks

1. A student conducted an experiment to measure the focal length of a concave mirror. During the
 experiment they measured the image distance corresponding to various different object distances and
 tabulated the results as follows.

 Object Distance (cm) 30 35 40 45 50 55 60
 Image Distance (cm) 61 46 40.5 35 34 31 29

 Draw a labelled diagram of the apparatus used in this experiment. (9)

Plot a suitable graph on graph paper and use the graph to find the focal length of the mirror. (21)

 Object Distance (u/cm) 30 35 40 45 50 55 60
 Image distance (v/cm) 61 46 40.5 35 34 31 29

How did the student obtain an estimate for the focal length of the mirror prior to setting up the
experiment? (7)

Why was it important to know this information and how did it influence the student in setting up the
experiment? (3)

2. A student conducted an experiment to show how the frequency of a stretched string depended on its
 length. The student noted that the tension in the string was 36 and they kept it at this value
 throughout the experiment. The results of the experiment are shown in the following table

 frequency (Hz) 256 288 320 341 384 426 480 512
 length (cm) 30.5 26.8 24.5 22.6 20.3 18.1 16.3 15.0

 Draw a labelled diagram showing how the student obtained the above data? (9)

Draw a suitable graph showing how the frequency of a stretched string depends on its length. (18)

 Frequency (Hz) 256 288 320 341 384 426 480 512
 Length (cm) 30.5 26.8 24.5 22.6 20.3 18.1 16.3 15

Use your graph to estimate the mass per unit length of the string. (9)

Why was it important that the tension remained constant throughout the experiment? (4)

3. A student conducted an experiment to find the resistivity of a piece of nichrome wire. During the
 experiment they measured the length, resistance and diameter of the wire.

 Explain clearly with the aid of diagrams how the student measured the length and resistance of the
 wire? (9)

 Resistance

 Length

The following data was collected by the student

 resistance 34.4 Ω
 length 72 

The diameter of the wire was measure at several different points along the wire to be

 0.21 , 0.2 , 0.22 , 0.19 and 0.21 

Use the data given to find the resistivity of nichrome wire. (12)

Outline an alternative method to measure the resistance of the wire. (9)

What effect (if any) would conducting the experiment on a warmer day have on the value of the
resistivity? (6)

Why was the diameter measured at several different points along the wire? (4)

4. A student conducted an experiment to show the characteristic curve for a semi-conductor diode. They
 first placed the diode in forward bias and noted the current for several different values of the applied
 potential difference. The results are shown in the following table

 Potential diff (V) 0 0.290 0.426 0.543 0.600 0.640 0.680 0.710
 Current (mA) 0 0 0.03 0.44 1.5 3.57 8.44 16.91

 Draw a clearly labelled circuit diagram showing how the student obtained the above data? (9)

Draw a suitable graph on graph paper and explain what you can deduce about the variation of the
current with potential difference in forward bias. (15)

 Potential diff (V) 0 0.290 0.426 0.543 0.600 0.640 0.680 0.710
 Current (mA) 0 0 0.03 0.44 1.5 3.57 8.44 16.91

Explain, with a clearly labelled diagram what chat changes would be made to the circuit to study the
variation of current with potential difference in reverse bias. (9)

Explain why an LED needs a protective resistor in series with it in a circuit whereas a photodiode does
not. (7)

Section B Answer ANY FIVE Questions from this Section 280 Marks

5. Answer any eight of the following (each part carries 7 marks)

 a) A 6V battery is connected to a 2.5 capacitor. What is the quantity of the charge stored?

 b) The half-life of an isotope is 1.5 Find the decay constant.

 c) The threshold frequency for a metal is 4.5 × 10!" . What is the work function?

 d) What is a semiconductor?

e) What is meant by timbre?

f) A person stands 8 away from a speaker emitting a sound at 1.9 What is the sound intensity

 where they stand.

g) Arrange the following in order of increasing wavelength

 Green Light , Radio Waves, Orange Light and Gamma Rays

h) A current of 1.2 A flows through a piece of wire of length 80 cm in a magnetic field of field strength

 3.5T Find the size of the force exerted on the wire?

i) Draw a diagram if the magnetic field produced by passing a current through a straight wire.

j) What massless quantity is emitted during beta decay?

6. Describe briefly a demonstration to show that sound is a wave motion. (9)

 A craftsman is designing a tin-whistle using a whistle and a hollow tube. The tin-whistle is to be in the
 key of C (frequency of lowest note is 256Hz) and a sketch of the instrument is shown below.

 Draw a diagram in your answer-book showing how a standing wave would form if the musician was
 playing the lowest note possible (lowest frequency). (9)

 Given that the speed of sound in air is approximately 340 m/s find the length of the tin-whistle ( )
 from opening to opening. (9)

What is meant by the Doppler Effect? (6)

Explain in terms of waves how the Doppler Effect occurs (9)

A person is playing the lowest note on the above tin-whistle while standing on a parade float travelling
at 10 m/s. What is the apparent change in the frequency observed by a person standing on the side of
the road watching the parade? (14)

7. Define what is meant by (i) Potential at a point

 (ii) Potential Difference

 (12)
 State Coulombs Law of charge. (7)

 A hollow metal sphere of radius 10 cm carries a
 charge of 2 mC as in the diagram to the right. A
 charge of 2 is placed at a distance of 15 cm 2 
 from the outer surface of the sphere as shown.

 Find 10 cm 15 cm 2 
 (i) The force experienced by the charge at P P
 (15)

(ii) The electric field intensity at P.

What is the field intensity at a distance of 8 cm from the centre of the sphere? (6)

Describe an experiment to demonstrate and electric field pattern. (9)

Describe an experiment to demonstrate point discharge. (7)

8. State Ohm’s Law? (6)

 Explain why it is more economical to transmit electricity at high voltages rather than low. (10)

In relation to the circuit to the right, find 12 

(i) The potential at A (12)
(ii) The potential difference

 200Ω
 100Ω
 between A and B (9)

 1000Ω 200Ω
(iii) The current flowing through the 1000Ω. A B

 (9)

 400Ω

Describe clearly the function and uses of an RCD? (10)

9. What is thermionic emission? (6)

 Draw a labelled diagram of a Cathode Ray oscilloscope. (12)

Draw a diagram of an X-Ray tube. (9)

The voltage in an x-ray tube is set at 120000V. What is the minimum wavelength of the
emitted x-rays? (12)

Why does the anode need to be made from a “heavy metal” in an x-ray tube? (7)

X-ray production can be viewed as the inverse of the photo-electric effect.
Explain the validity of this statement. (10)

10. Define what is meant by (i) Nuclear Fission?

 (ii) Nuclear Fusion

 (12)

 Explain why high temperatures are needed for nuclear fusion to take place. (9)

 Explain the operation of a nuclear reactor under the following headings (18)
 (i) Fuel

 (ii) Moderator

(iii) Control Rods

In 1932 the atom was successfully split for the first time. During the experiment a lithium target was
bombarded with protons. The collision of the protons with the lithium target caused the lithium to
undergo fission with the production of two alpha particles.

Write down a balanced nuclear reaction for the experiment. (7)

Calculate the energy released in the reaction. (10)

 Lithium Nucleus = 1.153 × 10!"# Proton= 1.674 × 10!"$ 
 Helium Nucleus= 6.64 × 10!"$ 

11. Define 1 ampere. (9)

 What is the principle upon which a moving call loudspeaker is based? (7)

 Describe an experiment to demonstrate this principle. (10)

Draw a labelled diagram of a moving coil galvanometer. (12)

A galvanometer has an internal resistance of 50Ω and can carry a maximum safe current of 5 . How
would this galvanometer be converted to

 (i) An ammeter reading up to 20 A.

 (ii) A voltmeter reading up to 100 V. (18)