(c) Gunda W. C. – 2017 PHYSICS DIRECTORY FOR FORM TWO

(c) Gunda W. C. – 2017 SUBJECT MATTERS TO COVER

(c) Gunda W. C. – 2017 1. STATIC ELECTRICITY CONCEPT OF STATIC ELECTRICITYElectric Charge (Electrostatic Charge) - A property of matter which causes it to experience a force when near other electrically charged matter Electrostatic Induction - A redistribution of the electrical charge in an object caused by nearby charges Electrophorus - A capacitive generator used to produce electrostatic charge by electrostatic induction Detection of charges - (Not found in exams) Conductors and insulators

(c) Gunda W. C. – 2017 Continue . . . Conductors - Materials which allow electricity to pass through them Conductivity - Is a measure of a material’s ability to conduct an electric current Insulator - A material which resists the flow of electric current. The electrons in the material are tightly bonded to their atoms Properties of an Insulator - Valence band and conduction band are far apart, forbidden gap is wide so that electrons cannot gain enough energy to jump across Explain the following observations - After a long flight, a plane may become charged - This is due to friction of the metallic body of the plane with the air and clouds

(c) Gunda W. C. – 2017 Continue . . .Capacity - The amount of charge a capacitor is able to hold Capacitor - A device which stores electric charge. It consists of a pair of conductors separated by an insulator. When there is a potential difference (voltage) across the conductors, a static electric field is created which stores energy Uses of Capacitors - Used for blocking direct current while allowing alternating current to pass, smoothing out power supplies, to tune radios to particular purposes Capacitance - The measure of the extent to which a capacitor can store a charge Factors affecting capacitance - Area of the plates, separation distance between the plates, strength of the dielectric material

(c) Gunda W. C. – 2017 Continue . . .Essential features of a capacitor - Two conducting plates, an insulator between the plates Alternating Current (AC) - The movement of electric charge periodically reverses direction Direct Current (DC) - The unidirectional flow of electric charge (flows only one way) Question 1. A capacitor is labeled with a capacitance value of 470μF and is charged to a potential difference of 10V. Calculate the charge stored by the capacitor

(c) Gunda W. C. – 2017 Solution

(c) Gunda W. C. – 2017 CHARGE DISTRIBUTION ALONG THE SURFACE OF A CONDUCTORLightning Conductor - A metal rod or conductor placed at the top of a building and is connected to the ground through a wire to protect the building from damage caused by lightningQuestion 1. Discuss the charge distribution on (i) The surface of a solid conductor of an irregular shape The charge density is higher at sharp points than at other areas

(c) Gunda W. C. – 2017 Solution(ii) A hollow conductor The charge is only on the outside surface of the conductor

(c) Gunda W. C. – 2017 Continue . . .Passengers in the plane are not charged, but an attendant who opens the door is at risk of becoming charged - This is because the inside of the plane is insulated, but when the door is opened the attendant is at risk of touching the body of the plane (iii) A lightning conductor as clouds pass over spikes on a house The charge density is higher at the end of the spikes, the cloud is negatively charged and the spikes are positively charged

(c) Gunda W. C. – 2017 Continue . . .2. (a) (i) What happens when a wire is connected to a charged capacitor? Also draw a diagram showing this. The electric current flows and the capacitor is discharged through the wire

(c) Gunda W. C. – 2017 Continue . . .(ii) An insulated plate A which has a negative charge is joined to a plate B with a positive charge by using a resistance wire. If a charge of 10-6C flows through the wire of resistance 2Ώ in 10-6 seconds, how much heat is dissipated in the wire?

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(c) Gunda W. C. – 2017 2. CURRENT ELECTRICITYCONCEPT OF CURRENT ELECTRICITY Current - A flow of electric charge or the rate of flow of electric charge (SI unit is ampere, and is measured using an ammeter) Electrical Conduction - The movement of electrically charged particles through a conductor Measurements used in circuits - Ampere (A), coulomb (C), volt (V), ohm (Ω), watt (W) Ampere (A) - A steady current which when flowing in two infinitely long, straight, parallel conductors which are 1 meter apart and have negligible areas of cross section cause a force of 2.0x10-7N per meter between the conductors Coulomb (C) - The quantity of charge which passes any section of a conductor in one second with a current a one ampere

(c) Gunda W. C. – 2017 Continue . . .Volt (V) - The p.d between any two points in a circuit where 1 joule of electrical energy is converted when 1 coulomb passes from one point to another Ohm (Ω) - The resistance of a conductor through which a current of one ampere is flowing when the p.d across it is one volt Watt (W) - SI unit of power which measures the rate of energy conversion which is defined as one Joule per second - When an electrical potential difference is placed across a conductor, its movable charges flow, giving rise to an electric current Simple electric circuits (Practical use of circuits, discussion of parallel vs series) *Note that this information is found in Magnetism

(c) Gunda W. C. – 2017 3. MAGNETISM CONCEPT OF MAGNETISMMagnetism - A force which is applied at an atomic or subatomic level whereby positive magnets and negative magnets attract one another Magnet - Is a material or object that produces a magnetic field Magnetic Materials - Materials which are attracted by a magnet and can be made magnets by artificial methods of magnetization (ex steel, cobalt, nickel, iron) Nonmagnetic Materials - Materials which are not attracted by a magnet and cannot be magnetized by artificial methods of magnetization (ex wood, carbon, plastic) Magnetic Field - A field of force produced by a magnetic object or particle or by a changing electric field

(c) Gunda W. C. – 2017 Continue . . .Magnetic Pole - A point which exists at or near each end of a magnet at which the attractive forces or repulsive forces of the magnet are concentrated Single Domain - Refers to the state of a magnet where magnetization does not vary across a magnet Magnetization - The process causing a material to become magnetic due to an external magnetic field Methods of making magnets - Stroking, induction, electrical Stroking Method - One pole of a magnet is rubbed against a metal rod to cause it to magnetize Induction Method - After a piece of unmagnetized metal is placed near or in contact with a pole of a magnet it will be magnetized Demagnetization - The causing of a material to lose its magnetic properties due to external forces or through decay over time

(c) Gunda W. C. – 2017 Continue . . .Magnetic Induction - The process of producing magnetism in a non-magnetized material when it is placed in a magnetic field Keepers - Prevents bar magnets from becoming weaker over time due to self demagnetization Neutral Point - A point in a magnetic field where the resultant field is zeroReason the strength of a magnet cannot increase beyond a certain limit - When all domains have been oriented in the same direction, no further magnetization is possible which means that the material is saturated Reason why an increase in temperature weakens or destroyed the magnetism of a magnet - Causes greater atomic vibration which prevents the domain from being aligned in the same direction

(c) Gunda W. C. – 2017 MAGNETIC FIELDS OF A MAGNET Magnetic Screening - The prevention of a magnetic field from reaching a certain region by surrounding the object with a magnetic material Magnetic Field - The region around a magnet where the effects of the magnet can be detected Question 1. Sketch the lines of force between two bars of magnets placed on a horizontal table with: (i) Their N-poles facing each other Note that the arrows always go towards an S pole or away from an N pole

(c) Gunda W. C. – 2017 Continue . . .

(c) Gunda W. C. – 2017 Continue . . .(ii) One N-pole facing the S-pole of anotherEarth’s magnetic field Earths magnetic field faces north

(c) Gunda W. C. – 2017 4. FORCES IN EQUILIBRIUM MOMENT OF A FORCEMoment - The tendency of a force to twist or rotate an object (torque). The SI unit is the Newton Metre Principle of Moments - If a body is in equilibrium under the action of forces which lie in one plane, the sum of clockwise moments is equal to the sum of anticlockwise moments about any point in that plane Center of Gravity - A point through which the resultant weight of all particles in the body appear to act Types of Equilibrium - Stable, unstable, neutral

(c) Gunda W. C. – 2017 Continue . . .Stable Equilibrium - When a body returns to its equilibrium position after being displaced slightly (Ex a sphere resting on a concave surface) Unstable Equilibrium - When a body does not return to its equilibrium position after being slightly displaced (a sphere resting on a convex surface)Neutral Equilibrium - When a body stays displaced after being slightly displaced and gravity exerts no moment about the base (a sphere on a flat surface) Why racing cars have wide wheel tracks - Increases stability because a wider base makes it more difficult to turn over

(c) Gunda W. C. – 2017 Question 1. A uniform half meter ruler is freely pivoted at the 15cm mark and balances horizontally when a body of mass 40g is hung at the 2.0m mark. (i) Make a clear sketch to show the forces and their positions in the arrangementSolution

(c) Gunda W. C. – 2017 Continue . . . (ii) Calculate the mass of the half-meter rulerThe clockwise moment will be on the right side because it moves the ruler in a clockwise direction. The left side is the anticlockwise moment because it moves the ruler in an anticlockwise direction. The moment is calculated by multiplying the length by the weight for each Clockwise moment = anticlockwise moment W x 10cm = 40gf x 13cm 10W = 520 W = 52g

(c) Gunda W. C. – 2017 5. SIMPLE MACHINESCONCEPT OF SIMPLE MACHINESMechanical Advantage - The factor by which a mechanism multiplies the force or torque applied to itVelocity Ratio (of a machine) - The distance that the point of effort moved divided by the distance that point of load moved

(c) Gunda W. C. – 2017 Continue . . .Efficiency - The ratio between energy used the total energy supplied. The excess energy is wasted, usually as heat energy1. A hydraulic press has a large circular piston of radius 0.8m and a circular plunger of radius 0.1m. A force of 200N is exerted by a plunger. (i) Find the force exerted on the piston. Also, state one reason why the weight of the load raised by the piston is much less than the force exerted on the piston.

(c) Gunda W. C. – 2017 Continue . . .

(c) Gunda W. C. – 2017 Continue . . .(ii) If the plunger is moved through a distance of 0.64m while exerting its force, what distance will the piston be raised? Given: Area of hydraulic press, AH = 2.011m2 Area of plunger, AP = 0.031m2 Height moved by plunger, hP = 0.64m Height moved by hydraulic press, hH = ? Volume = Area x Height Since the volume moved by the plunger equals the volume moved by the hydraulic press, we can set up an equation where they are equal to each other and use it to solve for the distance moved by the piston APHP = AHHH

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(c) Gunda W. C. – 2017 6. MOTION IN A STRAIGHT LINEDISTANCE AND DISPLACEMENT Uniform Velocity - A motion with zero acceleration in a given direction Uniform Acceleration - A constant rate of change of velocity Speed - Is the magnitude of an objects velocity, or the rate of change of an objects position. It is a scalar quantity with an SI unit of m/s Velocity - Is the measure of the rate of change of an objects position. It is a vector quantity with an SI unit of m/s in a certain direction Velocity Ratio (VR) - Distance moved by effort per distance moved by load

(c) Gunda W. C. – 2017 Continue . . .Terminal Velocity - Occurs when an object’s speed is constant due to the restraining force exerted by air (the maximum velocity of a falling object in air) Acceleration - The rate of change of velocity EQUATIONS OF UNIFORMLY ACCELERATED MOTION 1. 50g mass is placed on a straight track sloping at an angle of 45 to the horizontal as shown in the figure below. Calculate:

(c) Gunda W. C. – 2017 Continue . . .(i) The acceleration of the load as it slides down the slope Given: Mass, m = 55g Inclination, 45° Weight parallel to slope, mg Sin(45°) Weight normal to slope, mg Cos(45°)Normal reaction, R = mg Cos(45°) F = mg Sin(45°) g = 9.2 m/s2 a = ? Force Law:ma F = M AFirst we redraw the picture with this information

(c) Gunda W. C. – 2017 Continue . . .

(c) Gunda W. C. – 2017 Continue . . .(ii) The distance moved from rest after 0.2 seconds Given: u = 0 Time, t = 0.2 Acceleration, a = 6.93m/s2 Distance, S = ?

(c) Gunda W. C. – 2017 Continue . . .2. (a) Sketch the diagram of a body which starts from rest and accelerates uniformly for some time to a constant velocity and then maintains this velocity for a certain period of time before decelerating uniformly to a stop.

(c) Gunda W. C. – 2017 Continue . . .(b) A car moving with a uniform velocity of 100m/s is decelerated at 2.5m/s to a stop. Calculate: (i) The time taken for the car to stop Given: Initial velocity, u = 100 m/s Final velocity, v = 0 m/sa = -2.5 m/s2 t = ? This is equation means that the final velocity is equal to the initial velocity plus the acceleration over time v = u + at

(c) Gunda W. C. – 2017 Continue . . .(i) The distance traveled by the car before it is brought to rest Given: v2 = u2 + 2aD Distance traveled, D = ?

(c) Gunda W. C. – 2017 MOTION UNDER GRAVITYNewton - Unit of force where 1 Newton gives a body of 1kg an acceleration of 1m/s2 Conditions under which g can denote acceleration or the amount of force - Acceleration - For gravity g is represented in SI units as m/s2 under the condition that a body is undergoing free fall Force - For force g is represented in SI units as N/kg (force (N) per kilogram (kg)), under the condition that the mass is 1kg Force due to gravity on earth - 9.8 or 10 m/s

(c) Gunda W. C. – 2017 Question 1. (a) A rocket taking off vertical pushes out 25kg of exhaust gas every second at a velocity of 100m/s. If the total mass of the rocket is 200kg, (i) What is the resultant upward force on the rocket? Given: mrocket = 200kg v = 100 m/s vo = 0 m/s Newton’s Second Law of Motion: F = Rate of change of momentum

(c) Gunda W. C. – 2017 Continue . . .(ii) What is the upward acceleration of the rocket? Given: F = 2500N mrocket = 200kg a = ? Force Law: f = m a

(c) Gunda W. C. – 2017 Continue . . .(b) Calculate the acceleration of the rocket in (a) above when it has burned off 100kg of fuel To find the new mass of the rocket, you subtract the burned fuel from the original mass of the rocket Given: m = 200kg - 100kg = 100kg F = 2500N Force Law: f = m a

(c) Gunda W. C. – 2017 7. NEWTONS LAWS OF MOTION1st Law of motion 1st - Every body persists in its state of being at rest or of moving uniformly straight forward unless it is compelled to change its state by an outside force 2nd Law of motion 2nd - The rate of change of momentum of a body is proportional to the applied force and takes place in the direction of the force CONSERVATION OF LINEAR MOMENTUM Momentum - The product of the mass and velocity of an object. Its SI unit is kg*m/s

(c) Gunda W. C. – 2017 Continue . . .Principle of Conservation of Momentum - When bodies in a system interact, the total momentum remains constant provided that no external forces act upon the system Impulse - The change in momentum of a body when a force has been applied to it. Its SI unit is Ns (Newtons x seconds) 3rd Law of motion 3rd - To every action there is an equal and opposite reaction

(c) Gunda W. C. – 2017 8. TEMPERATURE CONCEPT OF TEMPERATURE Temperature - A quantitative measurement of hot or cold. Its SI unit is Kelvin (K) Absolute Zero - The temperature at which atoms stop moving, thereby causing the volume of a gas to drop near zero. It is measured as 0K Thermometer - An instrument which measures temperature Fundamental Interval of a Temperature Scale - The difference in temperature between the upper fixed point and the lower fixed point Upper Fixed Point - The temperature of steam from water boiling under standard atmospheric pressure of 760 mmHg

(c) Gunda W. C. – 2017 Continue . . .Lower Fixed Point - The temperature of pure melting ice under standard atmospheric pressure of 760 mmHg Advantages of mercury over alcohol as a thermometric liquid - Does not vaporize easily, expands steadily, Hg is a better conductor of heat, has a higher boiling point, does not cling to the glass inside the thermometer, it is opaque and easier to read Similarities between maximum and minimum thermometers - Perform one way measurement, contain steel indices

(c) Gunda W. C. – 2017 Continue . . .Differentiate between maximum and minimum thermometers - Maximum Thermometer - Records the maximum temperature reached during a certain period of time. It uses mercury in a glass thermometerMinimum Thermometer - Records the minimum temperature reached during a certain period of time. It uses alcohol in a glass thermometer 1. Determine the final temperature obtained when 500g of water at 100°C was mixed with 500g of water at 10°C and well stirred (Note: The specific heat capacity of water is 4200 J/(kg°C) >>>> NECTA 2007 4c Note that since the masses of the two samples of water are the same, you can just average the temperatures to get 55°C ((100+10)/2)

(c) Gunda W. C. – 2017 9. SUSTAINABLE ENERGY SOURCESWATER/SOLAR/WIND/SEA/GEOTHERMAL ENERGY Types of renewable energy - Wind, geothermal, solar, sea wave Wind Energy - Energy derived from the Earth’s winds Geothermal Energy - Energy derived from the internal processes of a planet Solar Energy - Energy derived from a stars radiant energy Sea Wave Energy - Energy derived from waves in the oceans Water Energy - Energy derived from falling water (ex. HEP) Anemometer - An instrument used for measuring wind speed Wind Vane - An instrument used for showing the direction of the wind