Radioactive decay Radioactive emission of alpha and beta particles and gamma rays take place due to radioactive decay. Radioactive decay is the process of unstable nuclei disintegrating to attain more stability. This process is not affected by: chemical combinations...
Uses of radioactive material Tracers: the ability of detectors to measure small quantities of radioactive materials is made use of in tracer applications. Tracers are widely used in medicine, industry and agriculture. Penetrating radiation: gamma rays are used to...
An atom contains three particles: electrons, and protons and neutrons which are located in the nucleus. The Geiger-Marsden Experiment In this experiment a beam of alpha particles is aimed at a thin piece of gold foil. A zinc sulphide screen mounted on a rotatable...
The total number of components of a nucleus is known as the nuclear or mass number (A). A nucleon is a proton or neutron. The number of protons are known is known as the proton number or atomic number (Z). Nuclide Notation If X represents an element containing A...
Einstein suggested that mass and energy are equivalent E = mc2. A change in energy, increase or decrease, will lead to corresponding change in mass, ∆m = ∆E/ c2 Nuclear fission The process whereby heavy unstable nuclide break up to produce energy. Nuclear fusion The...
Electromagnetic induction is used in the generation of electricity. The alternating current generator is an electromagnetic devise which transforms mechanical energy into electrical energy. Simple a.c. generator Consists of a rectangular coil of wire that is mounted...
A transformer is a device that changes a high alternating voltage at a low current to a low alternating voltage at a high current or vice versa. It is a useful device used for: electrical power transmissions from power stations to the consumer loads; regulating...
A metals atom contains outer electrons which move freely through the metallic material. These delocalised electrons are bound to the metal because of the attractive force of the atoms nuclei. However, when heated the electrons gain sufficient energy to escape from the...
The electron gun The electron gun produces a fine beam of electrons. It consists of a glass tube at a very low pressure. Electrons are produced by thermionic emission from a tungsten filament heated by a 6 V supply. A high positive potential is connected to a...
The Gold Leaf Experiment For this experiment a positively charged electroscope with a gold lead in a diverged position is used. A radium source is brought near to the cap of the electroscope. The radiation emitted ionises the surrounding air; as the cap is positively...
Resistor The resistor is used to measure the control the amount of current that flows through a circuit. The value and tolerance of the resistor is given by the four coloured bands on the resistor. The colours of the first three bands indicate the first digit, the...
Radioactive Decay Radiation is emitted by the nucleus of an atom. Un unstable nucleus emits radiation in an attempt to become more stable. This is known a radioactive decay. Nature of the radiation An alpha particle is a positively charged helium nucleus consisting of...
Fuse: The fuse is a devise which protects equipment from an excessive flow of current. When a fuse becomes hot and the current flowing through it is greater than it’s rated value, it melts. For safety precautions, fuses should have a rating which is slightly more than...
Current-Carrying Conductor in a Magnetic Field A current-carrying wire is surrounded by a magnetic field, and when this wire is placed in another magnetic field the two magnetic fields may interact and produce a force on the wire. This is called the motor effect. A...
Electromagnetic induction is the phenomenon of inducing an e.m.f. into a circuit due to a changing magnetic field. Faradays’ experiments i. Iron Ring Experiment: two coils of insulated copper wire are wound round a soft iron ring. The ends of coil A are connected to a...
The coil is connected to a split-ring commutator When current flows through the coil, the force acting on the coil will turn the coil in a clockwise direction until the coil is in the vertical position There is no current flowing in the vertical position, but due to...
A resistor determines the amount of energy capable of passing through, because the resistors material restricts the movement of electrons in the material. The resistance, R of a material is defined as the ratio V/I, where V is the potential difference across the...
In series The combined resistance is equal to the sum of the resistances The current is the same at all points around the circuit The potential difference of a power supply is shared between the resistors i.e. V = V1 + V2 + V3 In Parallel The effective...
Electricity can be dangerous in these situations: damaged insulation overheating of cables damp conditions Damaged insulation: All electrical appliances require two wires to complete a circuit, the live and neutral wires, starting from the voltage supply to the...
The electromotive force is described as the energy converted from non- electrical forms to an electrical form, when one coulomb of positive charge passes through the cell. The e.m.f. of a supply is the work done in moving one coulomb of charge around a circuit....
An electric current is a flow of charge. When a torch is switched on electrons flow through the torch bulb and cell. Metals contain delocalised electrons which move freely between the metal ions. The electrons prevent the positive ions from repelling each other....
The potential difference (p.d) between two points is defined as the energy converted from electrical to other forms when one coulomb of positive charge passes between the two points.
Patterns of Magnetic Fields A magnet field is produced when a current flows through a wire i.e. a current-carrying conductor produces a magnetic field. Straight Wire: Using a plotting compass the magnetic field pattern can be drawn. Place a wire upwards through a...
Matter is made up of particles called atoms which contain negatively charged particles called electrons that orbit around a nucleus of positively charged protons and neutral neutrons. An atom in its general state is balanced. An electrified state is that which is...
Electrostatic Charging by Friction Experiments: Rubbing a cloth and rod makes them electrically charged. This can be demonstrated by holding both the items near the hair – they attract the hair. Static electricity is generated by rubbing. Also, a charged object may...
Sound is a form of energy which travel as waves. Sound waves are produced by objects that vibrate in a medium. The medium can be a gas, liquid or solid. A vibrating object produces sound waves by the shifting layers of air particles. The vibrating object pushes and...
magnetic materials are attracted to the two ends of a magnet, called the poles; magnets have two poles, the south and north pole, the north-seeking pole points to the north and the south-seeking pole to the south; like poles repel and unlike poles attract.
Sound waves with frequencies above 20 kHz are called ultrasound, which exceeds the audible range for humans. Application In medical : Ultrasound is used to observe the internal parts of the body, especially in the development of a foetus. Ultrasound pulses are emitted...
A magnetic material is any material which feels a force when placed in a magnetic field e.g. cobalt, nickel, and a few alloys such as steel. A non-magnetic material is any material which does not feel a force when placed in a magnetic field e.g. brass, copper,...
Total internal reflection occurs when: The ray of light passes from a denser to a less dense medium; The angle of incidence in the denser medium is greater than the critical angle. The critical angle is defined as the angle of incidence in the optically dense medium...
Lenses can be divided into two types, depending on their shape: Converging lenses are fatter in the middle than at the edges; Diverging lenses are thinner in the middle than at the edges. Features of lenses: 1. The optical centre, C – the point midway between the lens...
The splitting up of white light into a spectrum is known as dispersion. White light is a mixture of all the different colours of the spectrum. In a prism, as white light enters, it slows down due to refraction which also means that its speed changes. Dispersion occurs...
All electromagnetic waves travel at the same speed and in a vacuum. They have the same speed as light – (3 × 108 m/s). Like light, the speed of electromagnetic waves depend on the material they travel through, and they travel the fastest in a vacuum. The...
All waves can be reflected, refracted and diffracted, and these behaviours can easily be observed with water waves. Reflection: When waves strike an interface between materials, they be reflected. A ripple tank can be used to demonstrate the reflection of water waves....
The reflection of a light ray can be investigates using a ray box and a plane mirror. The normal is the line drawn perpendicular to the mirror. The angle of incidence is the angle between the incident ray and the normal. The angle of reflection is between the...
The kinetic theory of matter describes the three states of matter, and the changes between them, in terms of the movement of particles. The main points are: all matter is made up of very small particles ; the particles are moving all the time ( the higher the...
Evaporation is the change of state from a liquid to its vapour at any temperature. Although both boiling and evaporation involve the change of state from a liquid to a vapour, there are important differences. Evaporation of liquid occurs due to molecules, at the...
Wave motion is activity that carries energy from one place to another without actually moving any matter. In wave motion, energy—the ability to perform work, or to exert force over distance—is transmitted from one place to another without actually moving any matter...
Crests and troughs: the top and bottom points reached by transverse waves. Wavelength (λ) : the distance from one wave crest or trough to the next. The SI unit for the wavelength is the metre (m). Amplitude: is the height of the wave crest or the depth of the trough...
Some common liquid-in-glass thermometers include: Thermocouple Thermometers A thermocouple thermometer consists of two wires made of different metals where the ends of the two wires are joined together to form two junctions. If the two junctions are at different...
Heat is the thermal energy that is supplied from the hotter object to the cooler object. The unit of measurement for energy is the joule. Energy is supplied to water when heated. It is transformed into the internal energy of the water molecules which is in two forms:...
Melting Melting is the process by which a solid changes into a liquid. The melting point is the temperature at which melting occurs; at a definite or constant temperature. A pure substance only melts at its melting point. The presence of impurities lowers the melting...
Boiling is the change of state from a liquid into a vapour, occurring at a constant temperature called the boiling point. The boiling point of a substance is the temperature of a substance at which it boils. During the process of boiling, the heat supplied to the...
Latent heat of fusion , Lf of a solid is the heat required to change it from solid to liquid state or vice versa without any change in temperature. The unit for Lf is the joule(J). The latent heat of an object depends on its mass. The specific latent heat of fusion,...
Thermal expansion is the expansion of a material when its temperature rises. Generally, solids expand the least, followed by liquids and then gases. Uses of expansion Rivets are used to join materials . A red-hot rivet is passed through holes in two metal plates and...
Matter is defined as anything that has mass and takes up space (volume). Matter exists in three physical states: *Liquids and gases are called fluids The three states respond differently to changes in temperature and pressure. They increase in volume with an increase...
Conduction is the transfer of thermal energy without any flow of the medium. Substances are made of tiny particles called atoms or groups of atoms called molecules. When a solid is heated the molecules begin to vibrate vigorously and bump into neighbouring molecules,...
Convection is the transfer of heat energy by means of a fluid (liquid or gas) through bulk movement of the fluid itself. When a fluid is heated it expands (particles take more space due to increased movement) which makes it less dense, so the hot fluid rises passes...
Radiation is the continual emission of infrared waves from the surface of all bodies, transmitted through space, without the aid of a material medium. Infrared radiation is absorbed by all objects and surfaces which experience a temperature rise. Infrared radiation is...
There are three main ways heat can be transferred into homes: Radiation: heat that travels from a heat source to warm a surface, e.g. sun radiation shining through a window heating the floor and furniture. Conduction: heat transferred through solid objects, e.g. heat...
Temperature is the measure of the degree of ‘hotness’ or coldness’ of a body. The temperature of a body is a measure of the average kinetic energy of its’ particles. Because it is the average kinetic energy of a particle, it does not depend on the size of the object....
Power is the rate of transfer of energy. The more powerful an appliance, the faster the rate at which hit transfers energy. The power of an appliance is measured in watts (W) or kilowatts (kW). 1 watt is a rate of transfer of energy of 1 joule per second (J/s). 1...
Pressure in gases is due to collisions of molecules with the walls on the container. If a container is closed and left to stand, it will not collapse because the air molecules in the container exert an outward pressure equal to that of the atmospheric pressure acting...
Different forms of energy include light, sound, electrical, elastic, nuclear, magnetic, mechanical (kinetic and potential) and chemical. Chemical energy is stored in fuel, food and batteries. This energy is released when chemical reactions take place (battery, food)....
Non-renewable energy sources Fossil fuels are formed in a process that takes millions of years. Fossils fuels are being used faster than they are being formed. They are called non-renewable energy sources because once they are finished they are none to replace it....
Nuclear fusion Nuclear fusion is the process of forcing two nuclei close enough together so they form a single larger nucleus. It can be brought about by making two light nuclei collide at a very high speed. Energy is released when two light nuclei are fused together....
All energy transfers waste energy. The efficiency of a device is a measure of the amount of energy that is usefully transferred. The energy transfers of a device can be represented using a Sankey diagram. Efficiency can be calculated using the energy or power...
Liquid column The taller the liquid column (with narrow base), the larger the amount of liquid contained, the greater the weight of the liquid to exert pressure The amount of pressure in the same liquid column is different at different depths. The greater the depth,...
Liquids are used in hydraulic systems to transmit forces from one part of a machine to another. Hydraulic Press An hydraulic press acts as a force multiplier. An effort force on piston A1 puts pressure on the liquid. The pressure is the same at all places in the...
Circular motion is movement along a circular path or a circular orbit. A body describing a circle is not at rest. It does not move with constant velocity because whether the speed is changing or constant, the direction of the motion continuously changes. From Newton’s...
Newton’s First Law Every object continues in its state of rest or uniform motion in a straight line unless a resultant force acts on it to change its state. This law states that if there is no resultant force acting on an object on rest, the object will remain at...
The mass of an object is a measure of the matter in it. It depends on the number of atoms it contains and the size of those atoms. This property cannot be changed by the location, shape and the speed of the body. The SI unit for mass is the kilogram (kg). Large masses...
The gravitational pull on an object is known as its weight. The gravitational field is a region in which a mass experiences a force due to gravitational attraction. The gravitational field strength, g, is defined as gravitational force acting per unit mass on an...
When we are comparing the masses of equal volumes of different substances, we are actually comparing their density. The density of a substance is defined as its matter per unit volume. Density = mass ÷ volume p = m ÷ v The SI unit for density is kilogram per cubic...
The centre of gravity of an object is defined as the point through which its whole weight appears to act for any orientation of the whole object. The centre of gravity is sometimes confused with the centre of mass. The centre of mass of an object is that point in a...
Stability is closely related to the centre of gravity (mass) of an object. Stability refers to the ability of an object to regain its original position after it has been tilted slightly. To increase the stability of an object: The centre of gravity should be as low as...
A force acting on an object may change its shape, size or direction. An elastic object regains its original shape when the forces deforming it are removed. Experiment The elasticity of an object can be measured by hanging weight form it. 1. The strip of material to be...
The turning effect of a force is called the moment of a force or torque. The moment of a force is defined as the turning effect of the force about a pivot, and is calculated by the product of the force F, and the perpendicular distance d, from the line of action of...
Friction is a contact force that slows down motion. Whenever the surface of an object slides over the surface of another object, each object exerts a frictional force on the other. This is because of the irregularities of the two surfaces. Even if there is no relative...
The acceleration of free-fall for a body near to the earth is constant. The acceleration is about 10 m/s2. Motions of bodies falling without air-resistance (vacuum): There is a constant (uniform) acceleration of 10 m/s2. The direction of the object is downwards,...
A force is a push or a pull that one object exerts on another which produces, or tends to produce, stops or tends to stop motion. A force can also change the shape of an object. The SI unit for force is newton (N), with 1N being the approximate amount of force that...
Balanced Forces When two or more forces acting on an object produce no resultant force, we say that the forces are balanced. From Newton’s First Law, we can deduce that the object is either stationary or moving at a constant velocity. Unbalanced Forces If there is a...
Scalar quantities are physical quantities which only possess a magnitude (size). A vector is a physical quantity with a magnitude and a direction.
The Metre Rule This instrument is commonly used in the laboratory to measure the length of wires or the distance between two points. Greater accuracy is attained by measuring from the 1.0 cm mark and then to subtract 1.0 cm from the result, because the zero mark is...
Due to different tome intervals that we wish to measure, we need different types of clocks and watches. Watches and pendulum clocks can be used to measure long intervals of time, and stopwatches and ticker tapes measure short intervals of time. Clocks are based on a...