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SS 3 Physics (1st Term)

physics Secondary

ELECTROMAGNETIC FIELD II

ELECTROMAGNETIC FIELD This is a field representing the joint interaction of electric and magnetic forces.  It is exerted on charged particles.  The force on a charge q moving with velocity v less than the velocity of light is given by F = q (E + v x B) A conductor carrying an electric current when placed in a magnetic field experiences a mechanical force. It can be demonstrated by using two metal rails fixed on each side of a powerful horse-shoe magnet.  A copper rod is placed across the rails.   When we pass current through this copper rod, it is observed that the copper rood rolls along the rails, towards the right.  If by adjusting the rheostat, we cause more current to flow through the rod, we will observe that the rod moves faster. Thus, the force on the rod increases when the current increases. Direction of the force –… Read More »ELECTROMAGNETIC FIELD II

physics Secondary

ELECTROMAGNETIC FIELD

PATTERNS OF MAGNETIC FIELDS Magnetic field pattern can easily be observed using iron fillings.  The magnetic is put on paper and the iron fillings are sprinkled lightly on the paper around the magnet.  The paper is tapped gently and the iron fillings are found to turn and set to in definite direction. MAGNETIC FIELD AROUND A STRAIGHT CONDUCTOR CARRYING CURRENT A straight conductor carrying current can be shown that it has magnet filed around it.  Allow a thick isolated copper wire to pass vertically through a hole in a card board shit.  As shown below, sprinkle some iron fillings uniformly on the cardboard around the vertical wire connect the ends of the wire to a battery, switch on the current and place some compass needles around the wire.  Note the direction to which the compass needle point.  Switch on the current and note the swing of the needles and how… Read More »ELECTROMAGNETIC FIELD

physics Secondary

MAGNETIC FIELD

MAGNET AND ITS PROPERTIES A magnet is any material that is capable of attracting other pieces of the same material as well as pieces of iron. A substance is said to be ferromagnetic if it is attracted by a magnet. Examples are iron, cobalt, Nickel, and certain alloys. Substances which cannot be attracted by a magnet are called non-magnetic material e.g. brass, wood, copper, and glass. Properties of magnets The ends of a magnet where the attracting power is greatest are called the poles. A bar magnet suspended freely in a vertical plane called magnetic meridian comes to rest with its axis in the North-South direction. The part which points northwards is called the north seeking pole or North Pole while the opposite pole is called the South Pole Like poles of magnet repel each other while unlike poles attract each other. The polarity of a magnet can be tested… Read More »MAGNETIC FIELD

physics Secondary

ELECTRIC MEASUREMENT

RESISTIVITY AND CONDUCTIVITY The resistance of a wire maintain at a constant temperature is related to its length L and its cross-sectional area (A) by the expression R = ρl A Where ρ is a constant known as resistivity of the material (its unit is ohm-metre, Ωm) ρ = RA l R = resistance, A = cross-sectional area, l = length of the wire. The resistance is the ability of a material to oppose the flow of current through it.  The greater the resistivity of a wire the poorer it is as an electrical conductor. That is why conductivity is used to specify the current –carrying ability of a material.  The greater the conductivity of a material, the more easily can current flow through the material.  Hence, materials with high conductivity will have low resistively. Conductivity, σ is the reciprocal of the resistivity σ = 1 ρ Electrical Conductivity:  This… Read More »ELECTRIC MEASUREMENT

physics Secondary

ELECTROLYSIS

DEFINITION OF SIMPLE TERMS Electrolysis – Is the process whereby a liquid conducts electricity by the movement of positive and negative ions within the liquid while undergoing chemical changes. Electrolytes – Are liquid, which allows the electricity through them is called electrolytes. Such electricity is salt solutions, alkalis and dilute acids (acidulated water).  Non-Electrolytes – are liquids, which do not allow electricity to pass through them. Such liquids include distilled water, alcohol, liquid paraffin and sugar solution. NOTE: Metals and hydrogen are deposited at the cathode, while non-metals and oxygen are deposited on the anode. The anode may dissolve in solution. Electrolysis does not manufacture electric charges and it is the “splitting’ of compounds by electricity. E.g. water decomposes into oxygen and hydrogen by electric current.   FARADAY’S LAWS OF ELECTROLYSIS Faraday’s first law sate that the mass of a substance liberated during the process of electrolysis is proportional to… Read More »ELECTROLYSIS

physics Secondary

ELECTRIC CELLS

ELECTRIC CIRCUIT Electric current is simply electric charge in motion. Electric cells are chemical devices, which are capable of causing an electric current to flow. This produces electric force, which pushes the current along. Electrons flow from the negative terminal or cathode of the cell to the positive terminal or anode TYPES OF ELECTRIC CELLS Electric cells are divided into two namely: the primary cells and the secondary cells PRIMARY CELLS – These are those cells in which current is produced as a result of an irreversible chemical charge. SECONDARY CELLS – These cells are those which can be recharged when they run down by passing current backwards through them. There are three components in a cell. Viz: The anode (positive electrode) The cathode (negative electrode) The electrolyte THE SIMPLE PRIMARY CELL (VOLTAIC CELL) A simple cell can be made by placing two different electrodes (metals) in an electrolyte. Two… Read More »ELECTRIC CELLS

physics Secondary

ELECTRIC FIELD

An electric field is a region of space which surrounds a system of electric charges. Electrical forces will act on any electric charge which is placed within the region.  Electric field is a vector quantity.  The direction of the filed can be determined using a test charge (a small positive charge) Fundamental Law of Electrostatics The fundamental law of electrostatic states that: “Like charge repels, unlike charges attract. COULOMB’S LAW Coulomb’s law states that the force between two point charges is proportional to the product of their charges and inversely proportional to the square of the distance between them. Mathematically, F α q1q2 r2 F =k q1q2 r2 Where k = 1 = 8.99×109 4πɛ◦ Thus, F = q1q2 4πɛ◦r2   ELECTRIC FIELD INTENSITY OR STRENGTH (E) The electric field intensity, E, at any point in an electric field is the force experienced by a unit positive test charge at… Read More »ELECTRIC FIELD

physics Secondary

GRAVITATIONAL FIELD

INTRODUCTION Gravitational field is a region or space around a mass in which the gravitational force of the mass can be felt. Gravitation is the force of attraction exerted by a body on all other bodies in the universe. Gravitational force act between all masses and hold together planets, stars and galaxies.  Each mass has a gravitational field around it. LAW OF UNIVERSAL GRAVITATION Newton’s law of universal of gravitation states that every particle in the universe attracts every other particle with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them M1 M2   K R The law can be expressed mathematically as: F ά M1M2                                         ………………… 1 F ά 1 r2                                                    ……………………2 F ά M1M2                                         ……………………3 r2 :. F = G M1M2                             ……………………4 r2 M1 and M2 are the masses of the two particles r is… Read More »GRAVITATIONAL FIELD

physics Secondary

ELECTROMAGNETIC WAVES

DEFINITION AND CONCEPT Electromagnetic waves are produced by electromagnetic vibrations. Electromagnetic waves have electrical origin and the ability to travel in vacuum.  So, electromagnetic waves are regarded as a combination of traveling electric and magnetic forces which vary in value and are directed at right angles to each other and to the direction of travel.  In other words, they are transverse waves. TYPES OF RADIATION The electromagnetic waves consist of the following: Radio waves with wavelength 10-3m to 1000m. Infra-red waves with average wavelengths of 10-6 Visible spectrum, known as light waves, with wavelengths of 7 x 10-7 m for red rays. Ultraviolet rays with wavelength of 10-8m X-rays with wavelength of 10-10 Gamma –rays with wavelength of 10-11 Radio waves: Radio waves have the longest wavelengths.  Radio waves are emitted from transmitters and carry radio signals to radio sets.  The shortest radio waves are called microwaves.  Microwaves are used… Read More »ELECTROMAGNETIC WAVES

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