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### 37 Cards in this Set

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 law of electric charges States that like charges repel and oposite charges attract. A charge is a force - a push or a pull. electric force is the FORCE between charged objects. Its strength is determined by two factors: 1-size of the charges 2- distance between the charges - closer = greater force conduction charging caused by DIRECT CONTACT induction charges get rearranged without direct contact conductor a material in w hich charges can move easily, like metal (copper, silver, aluminum and mercury), or water insulator a material in which charges cannot easily move because electrons are tightly bound to the atoms. Like plastic, rubber, glass, wood and air. Insulators protect you from shock. static electricity the buildup of electric charges on an object. electric discharge the loss of static electricity as charges move off an object. It can happen slowly or quickly like a shock or lighting friction rubbing two objects together can transfer electrons Conservation of Charge Charges are never created or destroyed - they just move from one object to another as the electrons move from one atom to another. The number of charges do not change. Who discovered that lightning was a form of electricity? Ben Franklin - key experiment How does lightning happen - different parts of cloud store different charges- bottom has negative charges. it induces positive charge on ground. Large charge difference causes rapid electric discharge Lightning rod a pointed rod connected to the ground by a wire. Lighting will strike the highest point first - closest. They are grounded, which means there is a path for the electric charges to go to the earth to be absorbed safely. prevent damage to buildings. Lightning danger anything sticking up higher than the ground is in danger of attracting lighting. cell a device that produces an electric current by converting CHEMICAL energy into ELECTRICAL energy battery also converts chemical energy into electrical energy - made up of several cells wet cells contain liquid electrolytes like a car battery, which u ses sulfuric acid as the electrolyte dry cells contain electrolytes that are solid or pastelike - in radios or flashlights potential difference A chemical reaction causes a difference in charge between the two electrodes, which means that an electric current can be produced by the cell to provide energy. The energy per unit charge or potential difference is measured in volts. The greater the potential difference, the greater the current. photocells the part of a solar panel that converts light into electrical energy. They contain silicon atoms, which emit electrins when they absorb light thermocouples Converts thermal energy to electrical energy. Make it by joining wires made of two different meatals into a loop, which causes charges to flow. current a continuous flow of charge, defined by the RATE at which the charge passes a given point. Higher the current=more charge passing the point each second. amphere a unit for the speed of the current, called amp for short. Symbol is (A) Direct Current DC - charges always flow in the same direction Alternating Current AC - charges constantly switch from flowing in one direction to flowing in the reverse direction voltage determines the current in a wire. it is the amount of energy released as charges move between two points in the path of a current. Another word for potential difference. Resistance the opposition to the flow of electric charge, expressed in ohms. It is "electrical friction". As resistance INCREASES, current DECREASES Good conductors have LOW RESISTANCE. Good insulators have H IGH RESISTANCE How do thickness and length of a wire affect the wire's resistance? thick wires have less resistance. so do short wires. How does temperature affect resistance? resistance increases as temperature increases. superconductor a cool metal that has almost no resistance Who invented this law that combines current, voltage and resistance? a german school teacher named Georg Ohm What is Ohm's law It says that current equals voltage divided by resistance give the formula for ohm's law ampheres (A) = volts (V)/ohms (Q) Electric power the RATE at which electrical energy is used to do work. The unit is called the WATT W = V x A Power ratings the amount of power needed to run something kilowatt used to express higher values of power Measuring household energy use Multiply the power in kilowatts by the TIME in hours - called kilowatt-hours or kWk