Electric Charges 2 Current + Charges PDF

Science quiz 2 Electric charges Electric charges are PHYSICAL property that leads to electromagnetic interactions between atoms. The unit of electric charge is Coulomb ( C ) the tiny particles that make up matter are called (atoms). All materials are made of atoms. Inside the...

Science quiz 2 Electric charges Electric charges are PHYSICAL property that leads to electromagnetic interactions between atoms. The unit of electric charge is Coulomb ( C ) the tiny particles that make up matter are called (atoms). All materials are made of atoms. Inside the atom there are three subatomic particles positive protons , neutral neutrons and outside negative electrons. Why are atoms uncharged? As number of +P = number of - e All matter has electrical charges. An object has 3 types of charges positive (+) charge, negative (–) charge, or neutral. An object that has no charge is called neutral. Law of electric charges states ‘LIKE CHARGES REPEL and Unlike charges attract. When you charge objects by any method, no charges are created nor destroyed. The region around a charged object where an electric force is exerted on another charged object is the electric field. How do charged objects within an electric field interact? Like charges repel , unlike charges attract. THE ELECTRIC FORCE IS THE ATTRACTION OR REPULSION BETWEEN CHARGED OBJECTS. or the force between charged objects is called ‘ electric force ‘ What two things affect the size of the electric force? Type of Charge and distance What two things affect the strength of electric force ? The size of charge and distance The smaller the distance, the stronger the electric force. The greater the distance , the weaker the electric force. Positive charged means lose electrons / Negative charged means gain electrons. Device is used to measure or to see object is charged is Electroscope Objects become charged when their atoms gain or lose electrons. Three ways that objects can gain or lose electrons are by:  1- Friction : Charging by friction occurs when two objects are rubbed together, or wiped together causing a transfer of electrons between the objects. Example :Your feet in socks and the carpet are doing charging by friction. 2- Contact or conduction : If a charged object and an uncharged object touch each other or contact each other. 3- Induction : A way of rearranging the charges within an object without touching it or near each other like A charged object is brought near a neutral object. Remember neutral objects are charged by induction Static electricity is THE BUILD UP OF ELECTRIC CHARGES. Static means = stationary or constant When you rub a balloon against your hair, electrons from your hair transfer to the balloon, which makes your hair positively charged due to electron loss. The balloon becomes negatively charged due to electron gain. When you hold the balloon several centimeters from your head, your hair stands up due to the attraction between the two opposite charges. The charges that build up on an object move off the object or sudden flow of charges is called: ‘ electric discharge ‘ or static discharge. an example of electric discharge on a small scale is a shock when you touch a metal doorknob after shuffling your feet on the carpet. an example of electric discharge on a larger scale are lightening and storm clouds. three things might you notice after an electric discharge like shock , flash , noise or lighting. How does lightning occur within a cloud? a rapid discharge of electricity between opposite charges from cloud to ground.( positive charge at top of cloud and negative charge at the bottom of cloud ) How do lightning rods protect buildings from lightning? Direct charges to other area to protect the building. Conductors are a material in which charges can move easily Example : Metals such as copper, aluminum, silver, and gold Water (when it contains dissolved salts ),Graphite (found in pencils) Human body (can conduct small amounts of electric current) Why are most metals good conductors? As electrons can move easily.  insulators are materials that resist the flow of charges. or a material in which charges CANNOT move easily Example : Rubber, Glass, Plastic and air , wood ,paper. What factors make a material a good insulator? No free electrons Semiconductors are materials that conduct charge better than insulators but not as well as conductors. This allows them to control the flow of charge. Example : Silicon. ELECTRICITY CAN PRODUCE MAGNETISM. MAGNETISM CAN CREATE ELECTRICITY. Electric current is used to create electromagnets.( electric current with magnet) An electromagnet is made by winding a copper wire around a steel rod and connecting the two ends of the wire to battery. When electricity runs through the coil, it creates a magnetic field which acts as bar magnet. An electromagnet is useful because the magnetic field can be controlled , it can be weaker or stronger field depending on electric current. Current (symbol I ) means the flow of electric charge or it is the flow of electrons through wire. Or is the amount of charge that passes a location in the wire every second. The flow of electrons along a wire is sort of like the flow of water through a pipe. The standard unit of current called the Ampere (A or amps). Two main kinds of current: alternating current (AC) and direct current (DC). Alternating Current, the flow of electrons is always changing directions and it is used in power lines and in household appliances. Direct Current, there is a constant flow of electrons along the circuit in one direction. It is used in batteries. AC is usually converted to DC using a device called a transformer. Electric Current is affected by two factors: 1- Voltage 2- Resistance An electric charge is “pushed” into wire by a force called voltage Voltage is the difference in electrical potential between two places. or Voltage is the amount of work required to move unit of charge between two points. Higher voltage produces a higher rate of flow of electric charges in a given wire. Voltage is measured in the unit volts (V). The opposition to the flow of electric charge is called resistance. Resistance is expressed in ohms (Ω, the Greek letter omega). Higher resistance at the same voltage results in lower current. Electrical insulators such as plastic have such a high resistance that electric charges cannot flow in them at all.