Electricity Notes PDF

# ELECTRICITY ## STATIC ELECTRICITY - **Definition:** The result of an imbalance between negative and positive charges in an object. - **Two types of electric charges:** - **Positive charge:** Objects have more protons (+) - **Negative charge:** Objects have more electrons (-) - **Neu...

# ELECTRICITY ## STATIC ELECTRICITY - **Definition:** The result of an imbalance between negative and positive charges in an object. - **Two types of electric charges:** - **Positive charge:** Objects have more protons (+) - **Negative charge:** Objects have more electrons (-) - **Neutral object:** An even amount of protons and electrons. Most objects are neutral until two neutral objects come into close proximity, causing the electrons to shift from one atom to another and become charged. - **Electrons are the ones mostly moving** because they are loosely bound together, and when acquiring energy can move faster - **Law of electric charges** - Like charges repel each other. - Opposite charges attract each other. - **Neutrons:** When a charged object is brought close to a neutral object, it causes the electrons in the neutral object to shift position (**induced charge separation**). This movement of electrons from a charged object to a neutral object (vice versa) is called **induced charge separation**. ## INDUCED CHARGE SEPERATION - This happens when a neutral object gives or takes electrons from a charged object when coming into close proximity. - **If the charged object is positively charged:** The neutral object will induce the electrons within itself to move toward the charged object. - **If the charged object is negatively charged:** It will induce the electrons within itself to move away from the object, meaning the positive protons are close to the object. ## ELECTROSCOPES - There are two types of electroscopes: - **Pith ball electroscope:** Used to test for the type of electric charge. - **Metal leaf electroscope:** Detects electric charge, and is more sensitive to electric charge. ## VOCABULARY - **Static electricity:** Imbalance of electric charge on the surface of an object. - **Electric charge:** An atom that does not have an equal number of protons and electrons. - **Neutral charge:** Equal number of protons and electrons. - **Negatively charged:** More electrons than protons. - **Positively charged:** More protons than electrons. - **Electroscope:** Used to detect electric charging. ## CONDUCTORS & INSULATORS - **Conductors:** Materials that allow the movement of electrons - **Insulators:** Materials that inhibit or restrict the flow of electrons - **Examples:** - **Conductors:** Wiring, electrical cords, lamps, walls. - **Insulators:** Insulative tubes. ## STATIC ELECTRICITY- CARGING OBJECTS - There are three ways to charge an object: 1. **Friction:** Rubbing two objects can cause one to lose electrons and the other to gain electrons. 2. **Contact:** Bringing a charged object into contact with a neutral object will cause the neutral object to become charged 3. **Induction:** Bringing a charged object close to, but not touching, a neutral object can charge an object using induction. - **Electrostatic series:** The object with a strong hold of electrons will get negatively charged and the object with a weak hold on electrons gets positively charged. ## DISCHARGE - There are 3 ways to neutralize objects: 1. **Grounding:** Connecting an object to earth using a conductor. Earth can accept or give lots of electrons without much effort, because it is neutral. This prevents electrons from building up and creating sparks. 2. **H₂O Vapor:** When water molecules collide with objects, electrons are transferred to the water molecules. This causes the charged object to lose its charge. The reason for this is that objects become charged easier in the winter, since the air is less humid and objects don't get neutralized as easily. 3. **Electric discharge:** A rapid transfer of electric charge from one object to another when two charged objects are brought together. Electrons move from the more negatively charged object to the less negatively charged object. The bigger the charge imbalance, the larger and more noticeable the discharge is. ## ELECTRICITY ### LIGHTNING - **What causes lightning?** 1. When thunderclouds form, negative charges concentrate near the bottom of the cloud. Electrons on the ground are repelled and the ground becomes positively charged. 2. A huge spark (lightning) may form between the cloud and the ground if the charge imbalance becomes great enough. Electrons are then rapidly transferred from the cloud to the ground in the form of a lightning bolt. 3. **Thunder is a result of lightning**, as the electrons superheat the surrounding air and thunder is formed 4. **Lightning can cause:** - **Forest Fires** - **Building Fires** - **Stops heart of respiration** - **Death** ### LASERS PRINTERS - **How do laser printers work?** - A laser is used to create a negative (-) image on a positively charged drum. - The drum is rolled over toner. - Toner particles are positively charged and are attracted to the negatively charged image areas on the drum. - The drum is rolled over paper. - The positive (+) toner is attracted to the paper. - The toner is heated and bonded to the printer. ## ENERGY & ENERGY TRANSFORMATIONS - Energy can be changed or transformed from one form to another. - **Types of Energy:** - Mechanical energy - Electric energy - Radiant energy - Sound - **Bulb efficiency:** Can be measured by dividing the power used to the amount of light produced. - **Incandescent bulbs:** Only have a 5% efficiency. ## ELECTRIC CIRCUITS - **Current electricity:** The controlled flow of electrons through a conductor - **Electrical energy:** The energy provided by the flow of electrons in a circuit. - **Components:** Cell, bulb, switch, motor, resistor, ammeter, voltmeter, wire. - **Battery:** (Also called a cell). The energy source of the circuit, which charges the electrons. Inside the battery chemical reactions take place (chemical energy into electrical energy). - **Switch:** Controls the flow of electrons in the circuit. - **Wire:** Transports the electrons in the circuits. - **Load:** Usually refers to the object being powered in the circuit (for example: Light bulb, motor, fridge). ## SERIES & PARALLEL CIRCUITS - **Series circuit:** Only one path for the electrons to flow through. Every electron must go through every load. - **Parallel circuit:** More than one path for the electrons to flow through. Each electron has a choice of path. ## CALCULATING CURRENT & CHARGE - **Formula:** - Current = Charge moving past a point / time - I = Q / t - I = Amperes (A) - Q = Coulombs (C) - t = Time (seconds/s) ## ELECTRIC CURRENT - Electric current is the rate of electron flow past a certain point in the circuit. - It is measured in amperes (A). - 1A = 1000 mA ## POTENTIAL DIFFERENCE - **What is potential energy?** - Potential energy is "stored energy." It has the potential to do something later on. - **Potential difference:** - Potential difference is the difference in energy between a point in the circuit. - It is measured in volts (V). - **Formula:** - Potential difference = Total energy/amount of charge - V = E/Q - V = volts (V) - E = joules (J) - Q = coulombs (C) ## RESISTANCE - **Length of wire:** As the length of the wire increases, resistance increases. - **Area of cross section:** The thicker the wire, the lower the resistance. - **Temperature:** As the temperature increases, resistance decreases. - **Type of material:** Conductors have a lower resistance than insulators. ## OHM'S LAW - Ohm's Law states that as the resistance of the load increases, so does the current. ## ELECTRICITY - **Formula:** - V = IR (Voltage = Current * Resistance) - V = Voltage (potential energy) (Volts/V) - I = Current (Amperes/A) - R = Resistance (Ohms/ Ω) ## EXTRA - **Ammeter:** Counts the number of electrons passing a specific point in a circuit and, using this data, it calculates the current. - **Voltmeter:** Calculates the potential difference (voltage) by counting the number of electrons in two different points across the circuit. It only works if there is a change in current (example: battery/load).