SCIE 4001
Section A - Multiple Choice
Section A - Multiple Choice Answers
Multiple Choice on Section B Matter and Materials
Multiple Choice on Section B Matter and Materials Answers
Section B - Matter and Materials
Section C - Energy
Section D - Structures and Mechanisms
 

Unit 2 Energy

QUESTION

Three steel knitting needles A, B and C are supplied to you. Two of them are magnetized while the third one is not.
(a)Describe how you would identify them if no other apparatus is available. (3 marks)
(b)What do you understand by the following terms? (4marks)
(i) A direct current (ii) An alternating current (iii) An open circuit (iv) a fuse. 
(c)A student uses a “slingshot” to shoot pigeons. How does the stone used to shoot the pigeon get its energy? (2marks)
(d) Explain fully what you understand by the process of convection in a liquid. (4marks)
(e)Write down two (2) properties of sound. (2marks)

Answer Points

(a) (i) Magnets have two poles: like poles repel and unlike poles attract
(ii) Magnets attract magnetic materials (usually iron based)
(iii) The only true test for an object being a magnet is if it repels another magnet.
(iv) Try bringing the ends of the needle together in pairs (XY. XZ and YZ). Switch the ends of the pairs. The two that repel each other are magnets

(b) (i) Direct current flows in one direction only (conventional current flows from positive to negative)
(ii) Alternating current flows back and forth. (Our mains has a.c. reversing itself 60 times per second)
(iii) Open circuit is one which has a break through which current cannot flow.
(iv) A fuse is a device to prevent overload of current in a circuit. It burns out if the current exceeds its rated value.

answers(c) The rubber has stored up energy (mechanical potential). When it is released and the ‘tongue’ moves it is transferred to the stone as mechanical kinetic energy.

(d) (i) Convection is the transfer of heat through a process where the liquid itself moves.
(ii) When the bottom of the liquid is heated it expands and thus gets less dense than the colder liquid.
(iii) The hot (less dense) liquid rises and cold liquid rushes in to take its place
(iv) The continuous cycle of movement is called a convection current

(e) Sound is energy transferred as
(i) waves
(ii) whose speed depends on the medium (solid, liquid, gas – fastest to slowest)
(ii) the loudness of a sound is the amplitude of the wave
(iii) the pitch is the frequency of the sound

 

Unit 2 Energy

QUESTION
(a)Draw circuit diagrams to show (i)   a dry cell connected to three lamps in series. (2 marks)
(ii) a dry cell connected to three lamps in parallel. (2 marks)
(b) In old western movies, bandits planning to raid a train were observed putting their ears on the railway line.
How do you think such action assisted them to plan their ambush? (3marks)
(c) A person speaking in a microphone is heard by the audience through a loud speaker. What are the energy changes taking place? (2 marks)
(d) Explain how conduction takes place in a solid. (3marks)
(e) An Amerindian fisherman tried to spear a fish in a stream but missed it. (i) Why do you think he missed the fish? (1mark)
(ii) Draw two rays from a point on a fish in a stream where someone on the bank must aim to spear the fish. (2marks)

Answer Points

answer2 answer 2
(a)(i) Bulbs in Series
(a)(ii) Bulbs in Parallel

(b) Sound travels faster along the metal of the tracks than through the air, so they will hear the noise of the approaching train through the track before hearing it through the air giving them some extra time.

(c) Sound (speech) → mechanical kinetic energy (vibration of the coil in the microphone) → electrical energy (in the circuits) → mechanical kinetic energy (the movement of the speaker cone) → sound energy (the sound heard) → mechanical kinetic energy (vibration of ear parts).

(d) Conduction of heat energy and electrical energy take place by movement of ‘free’ electrons. In conduction of heat energy the energy is also passed from atom to atom by vibration. Sound energy is conducted by waves through materials.

(e) (i) The non-scientific answer (and it will get no marks) – he did not aim properly). The scientific answer is that he aimed at where he saw the fish which is a different position from where it is because of refraction of light as it leaves the water and goes through the air.

answer2
(e) (ii)

Unit 2 Energy

QUESTION

(a) A little boy wanted to throw a 5 cents into a pool for good luck! He mistakenly threw his 25cents for candy into the pool.The boy fell into the pool while trying to retrieve his money for candy. Use rays of light to explain why the pool appeared shallower. (4 marks)
(b) Explain the behaviour of light which makes an object appear to be in a position other than where it actually is. (3 marks)
(c) With the aid of diagrams explain the difference between light bulbs connected in series and light bulbs connected in parallel. (6 marks)
(d) What is tha advantage of connecting light bulbs in parallel? (2 marks)

answer
(a) (i) Solid arrows used to show two light rays from the coin.
(ii) These rays bend at the surface (still solid and at away from the direction it was going) to enter the eye.
(iii) Rays projected backward (using dotted lines) to locate the image (at the intersection of the rays)
answers
(b)

(b) Answer points–
(i) Light rays travel in straight lines.
(ii) The rays are bent away from the direction in which they were going (called bent away from the normal- the red line)
(ii) The eye sees the coin in the new position where the rays that enter the eye intersect when projected backwards.
(iv) Since the rays are bent away from the normal the projection appears closer to the surface than the actual coinAnswer points–
(i) Light rays travel in straight lines.
(ii) The rays are bent away from the direction in which they were going (called bent away from the normal- the red line)
(ii) The eye sees the coin in the new position where the rays that enter the eye intersect when projected backwards.

answer

(c) Answer points–
(i) Circuits must be complete (no breaks. Recall the switch symbol is NOT a break)
(ii) Symbol for bulb has a complete circle with a complete connected path to the filament)answer
(iii) This particular battery has two cells answer
(iv) Bulbs in series have no branches.
(vi)  Bulbs in series have the same current.
(vii) Bulbs in parallel are branched.
(viii) Bulbs in parallel share total current and may have different currents.

(d) Answer points–
(i) Bulbs in parallel may be connected by independent switches while a switch in a series circuit turns off ALL bulbs.
(ii) Bulbs in series go out when one burns out while bulbs in parallel (other branches) remain ON.
(iii) A defect in the parallel branch of a circuit will not affect the other branches.

 

(c)

 

 

     
Concept by Kishore Lal. Programmed by Kishore Lal... Copyright © 2015 Kishore Lal. All rights reserved.