Rational Functions (A)
Month: February 2021
Explain how combustion engines produce nitrogen oxides.
Fuels are combusted in internal combustion engines, producing a lot of heat.
The high temperature condition causes oxygen and nitrogen in the air to react to form oxides of nitrogen.
Describe the effect of temperature increase on the resistance of a metallic conductor.
The resistance increases as the temperature of a metallic conductor increases, so the resistance is directly proportional to the temperature.
When temperature increases, the amplitude of vibration of atoms increases. As a result, the number of collisions among the electrons and atoms increases, increasing the resistance to the flow of charges through the conductor.
Describe the pollution problems caused by the disposal of non-biodegradable plastics.
– Plastics are flammable.
In the event of a fire, plastic materials burn readily, causing the fire to spread quickly.
– Burning of plastics gives off toxic gases.
Many plastics produce poisonous gases upon incineration, causing air pollution.
– Plastics are non-biodegradable.
By “non-biodegradable”, it means that plastics cannot be decomposed by bacteria in the soil. Improper disposal of plastics can cause land and water pollution.
Describe what is meant by “wave motion”.
A wave motion is a movement or a disturbance through a medium, where the individual particles in the medium only vibrate vertically, horizontally, or in a cyclical pattern.
The wave motion can be illustrated:
– In a rope, when one end of a rope is moved in an up-and-down motion in a cyclical pattern.
– In a spring, when the spring is moved in an up-and-down motion, or a back-and-forth motion, in a cyclical pattern.
– In a ripple tank, when the dipper is moved in an up-and-down motion on the water surface, producing water waves.
What are the applications of esters?
Esters are used:
– in the manufacture of perfumes
– in the manufacture of artificial food flavorings
– as solvents for cosmetics and glues
– in the manufacture of soaps
Why must the temperature be kept at 37 deg C during fermentation of glucose solution?
At 37 deg C, the enzymes in yeast are the most active, so fermentation process will be fastest.
At low temperatures, the enzymes in yeast are inactive, so fermentation will be slow.
At high temperatures, the enzymes in yeast will be denatured, so fermentation will stop.
Movement of electrons in discharge ball
An electrostatic generator is used to produce sparks as shown below.
The belt carries negative charges to the dome, making it negatively charged. Before a spark is produced, the discharge ball becomes positively charged.
Describe and explain the movement of electrons in the discharge ball and in the conducting rod as the ball becomes charged.
The electrons in the discharge ball and in the conducting rod moves downwards through the conducting wire, and to the ground.
Electrostatic charging by induction occurs in the ball and rod as they are placed near to the negatively charged dome. Like charges repel, causing the negatively charged electrons in the ball and rod to move away from the dome, escaping through the conducting wire to the ground.
Movement of air particles in sound waves
A sound wave in air is illustrated below.
Points A, B, C and D are all the centers of regions of compression in the sound wave.
Describe what happens as one complete sound wave moves past a point.
The particles in the air are disturbed by the sound waves and vibrates to and fro, in a direction parallel to the direction of the sound waves.
An air particle in the sound wave will vibrate from its rest position to the left, until it reaches its maximum displacement to the left, then vibrate towards the right, move past its rest position, until it reaches its maximum displacement to the right. Then it vibrates to the left, until it returns back to its original rest position to complete one wave motion of the sound wave.