Presentation Transcript

1. Electricity and Magnetism

2. Investigation 1 Electricity and Magnetism
3. Electricity Circuit- is an uninterrupted path between the terminals of a power source. Batteries are a power source for circuits, sources of chemical energy Each terminal is connected to a different type of chemical Chemical at the negative end release electrons Chemical at the positive end attracts the electrons Electrons flow from the chemical with higher electric potential to lower electric potential Electric Potential is the potential energy per unit of positive charge, measured in volts Voltage is the difference between the two electric potentials, measured in Volts
4. Electricity Electrons flow from negative to positive terminals in a battery a current flows from the positive terminal to the negative terminal Current is the flow of electrons through a circuit Measured in Amps (A) When Circuits are created, electrons begin to flow through the circuit, some of the material that make up the circuit may slow the flow of the electrons
5. Circuits Circuits contain a power source, paths for the current to flow, and one or more resistors. A Resistor is a device in a circuit that slows the flow of electrons Resistance is used to determine the effect of resistors on the flow of current Resistance in measure in units called ohms (Ω)
6. Schematic Schematics are used to represent a circuit. Shows what components of the circuit are needed and where to put each component Special symbols are used to represent the components of the circuit Indicates where any meters should be placed Different meters can be represented by what they should be measuring ( V- voltmeter, A- Ammeter) “I” indicates the direction of the current flow
7. Schematic
8. Schematic
9. Ohm’s Law Relationship between voltage, current and resistance Change in the Current is proportional to the change in voltage when resistance is held constant
10. Ohm’s Law Ohm’s Law expresses the relationship between voltage, current and resistance V=IR R= V/I V= voltage in volts I= current in amps R= resistance in ohms Ω
11. Investigation One Resistor A Resistor B Relationship between the voltage and the current As the voltage increased the current increased Relationship between the voltage and the current As the voltage increased the current increased There was a Direct Relationship between the current and the voltage.
12. Investigation Two
13. Electrical Wire Rated by the amount of current it can safely carry Determining a wire’s ability to handle a specific electrical load is by its composition or dimensions of the wire
14. Resistors When two resistors are placed end to end or in series, they can be thought of as making a single resistor with a greater length. When two resistors are placed in parallel, Cross- sectional area) the effect on resistance is similar to using a resistor with a larger diameter.
15. Resistors and Current Resistor Length Cross-Sectional Area Resistors in Parallel Increase in cross-sectional area Current increases Resistance decreases Decrease the cross-sectional area Current decreases Resistance increases Increase in resistor length Current decreases Resistances increase Decrease in resistor length Current increases Resistance decreases
16. RESISTANCE Ratio between the voltage and the current in a circuit As voltage changes, current changes in proportion to the voltage. Resistance remains constant.
17. Investigation Three
18. Magnetism Magnetism is a property of matter Some metals can be permanently magnetized iron
19. Electromagnetism Others temporary Created by wrapping coil of wire around a piece of metal and passing an electric current through the wire Metal remains magnetic as long as the electrical current is flowing Electromagnet-flow of electric current (I) creates a magnetic field that is perpendicular to the current path or wire
20. Temporary Magnetism Magnetic Crane- moving scrap metal "Destroying the Evidence"
21. Electromagnetism Strength of an electromagnet is determined by the size of the magnetic field Magnetic field is reported in units of Tesla, T Formula for the size of a magnetic field B=μ₀ x n x I B is equal to mu sub zero times n times I B= magnetic field μ₀=4π x10⁻⁷ Tesla-meter/amps (constant) μ₀= 21.57 x 10⁻⁷ n= N/L ( N= number of turns of wire, L=length of coil) I = current in amps
22. B=μ₀∙n ∙I The formula shows that the current is directly related to the strength of the magnetic field Increasing # batteries= increase in current Increasing # batteries =increased strength of the magnetic field By increasing the current Decreasing the current= decrease in magnetic field
23. B=μ₀∙n ∙I Magnetic field increases when the current, the number of turns of the wire, or the length of the coil is increased
24. Relationship Between Electricity and Magnetism The flow of current through a wire generates a magnetic field perpendicular to the wire. As the amount of current increases the magnitude of the magnetic field increase Current increases= magnetic field increasing
25. Factors that affect the strength of an Electromagnet # of turns of wire in the coil over a specific length Amount of current flowing through the wire Increasing current= increases the strength of the electromagnetic Decreasing current= decreases strength of the electromagnet As the number of turns of a wire in a coil increases the strength of the electromagnet increases Decreasing # of turns decreases the strength of the magnetic field
26. People to know
27. André-Marie Ampère One of the main founders of the science of classical electromagnetism Ampère showed that two parallel wires carrying electric currents attract or repel each other, depending on whether the currents flow in the same or opposite directions. Ampère’s law -states that the mutual action of two lengths of current-carrying wire is proportional to their lengths and to the intensities of their currents.  The unit Amp (Ampere) is named after him
28. Alessandro Volta Invented the battery in the 1800s. The battery made by Volta is credited as the first electrochemical cell. It consists of two electrodes: one made of zinc, the other of copper.  The unit of Voltage, V, is named after him
29. Georg Simon Ohm Began his research with the new electrochemical cell, invented scientist Alessandro Volta. Found that there is a direct proportionality between the potential difference (voltage) applied across a conductor and the resultant electric current. This relationship is known as Ohm's law.
30. Nikola Tesla Best known for his contributions to the design of the modern alternating current(AC) electricity supply system. Immigrated to the US and worked for Thomas Edison before starting his own business Tesla, SI unit measure for magnetic field strength.