Topic 1: Electric Charge How does an object get a charge (must gain or lose something)? What does it mean when an object is positively charged? What about negatively charged? An object gets a charge when it is rubbed. This rubbing causes the objects to gain or lose electrons. When it loses electrons it becomes positively charged. When an object gains electrons it becomes negatively charged. What is an object called when it has an even number of positive and negative charges? It’s called balanced or NEUTRAL What are the THREE LAWS OF CHARGES? (page 268) 1. Unlike charges attract 2. Like charges repel 3. Charged objects attract uncharged objects. Define STATIC ELECTRICITY: The unbalance of electrons created by rubbing or friction in which electrons do not move. Define INSULATOR and provide an example: Doesn’t allow electrons to move through it easily. Define CONDUCTOR and provide an example: Allows electrons to move through it easily. Define SEMICONDUCTOR and provide an example: Materials with higher conductivity than insulators but lower conductivity than conductors. Define SUPERCONDUCTOR and provide an example: Materials that offer little resistance to no resistance to flow of charges. See page 269 bottom paragraph. Define GROUNDING: Connecting an object to Earth with a conducting wire. This neutralizes the charges. Describe NEUTRALIZATION: Becoming balanced. Topic 2: Electricity Within a Circuit Define CIRCUIT: A continuous pathway for charges to move along. All circuit diagrams have four basic parts. Name them, and describe what they do. 1. Source: Battery, cell etc 2. Control: Switch that can allow the electrons to follow or not on a complete path 3. Load: Converts electrical energy into other forms of energy (a resistor symbol also can represent this) 4. Conductor: Wire or substance that allows electrons to follow along them Define BATTERY: two or more cells connected together Define SWITCH: opens or closes a circuit to control the current Define RESISTOR: hinders the motion of electric charge and converts electric energy into other forms of energy Define LOAD: converts electrical energy into other forms of energy Draw the circuit diagram symbols for the following. See the bottom of page 273 single cell lamp battery switch conductor resistor Define CURRENT: The amount of charge that passes a point in a conducting wire every second. What is the SYMBOL for current? I What is the standard unit of measurement for electric current (two units)? ampere (A) or milliampere (mA) An instrument used to measure very weak electric current is called a(n) galvanometer while larger currents are measure with a(n) ammeter or a(n) milliammeter. Define VOLTAGE: (potential difference) The difference in energy per unit of charge between one point in the circuit and another point in the circuit (this causes the PUSH or FORCE to get electrons moving). Voltage is also referred to as POTENTIAL DIFFERENCE (two words). What is the SYMBOL for voltage? V What is the standard unit of measurement for voltage? volt An instrument used to measure voltage is the VOLTMETER. When measuring voltage, you are measuring the difference between 2 different points. Match the water related terms from the left column to the terms on the right that best classifies each electric term. a. load à 4. water wheel b. switch à 5. valve c. electric current à 6. flow rate d. voltage à 2. pressure e. battery à 1. pump f. conductor (wire) à 3. pipe A device that can measure voltage and current is called a MULTIMETER. .