University:
Boston University
Course:
CAS PY 242 | Principles of General Physics 2
Academic year:

2021
Views:

482

Pages:

24
Author:

Emerson Gould

Electricity and Circuits I don’t get electricity jokes. Watts so funny about them? “... the set of physical phenomena associated with the presence and motion of electric charge” (Wikipedia) Electricity In other words… A form of energy caused by charged particles What does a light bulb eat for fresh breath? The Energy Theory The Conservation of Energy states that energy cannot be created or destroyed, only altered from one form to another. Fila-mint! Positive vs. Negative Charge Positive charge = lose electrons Negative charge = gain electrons Static - particles stay together Static vs. Dynamic Dynamic - particles move in same direction Voltage voltage - measure of energy between two points ● ● ● supplied by a battery/power supply measured in Volts (V) can be measured using a voltmeter vs. Current current - direction of the flow of charged particles ● ● flows from positive to negative potentials measured in Ampere (amp) Direct and Alternating Currents What’s an electrician’s favorite ice cream flavor? Circuits circuit- a closed path where electricity flows where a battery is energy source Shock-a-late ❏ ❏ Schematic Diagram ❏ shows the layout of a circuit uses symbols for the electrical components instead of realistic pictures shows current, voltage, and resistance ❏ ❏ ❏ I = current V = voltage R = resistance Circuit Components ● ● parts of a circuit loads (such as resistors, capacitors, and inductors) Resistors resistors - controls the current flowing through a circuit ❏ ❏ ❏ ❏ less resistance = more current measured in Ohms (Ω) Related to Ohm’s Law (V=IR) color strips around resistor tell the amount of resistance Capacitors capacitors - two charged plates (positive and negative) that resist sudden shifts in the Voltage ❏ ❏ when fully charged, the current stops because it becomes an open circuit stores energy in an electric field Inductors inductors - a coil that stores energy in the form of a magnetic field and resists sudden changes in the current Switches switch- a component that opens and closes ● ● can be used to open and close a circuit light switch- when you turn the light on, you close the circuit, vice versa What kind of car does a electrician drive? Circuit Properties Volts-Wagon!!! Open Circuit ● Open circuits do not allow an electrical current to flow through the circuit. ○ Air is not a good conductor, therefore the electricity cannot flow through to the next component or wire. vs. Closed Circuit ● Closed circuits are complete and allows electricity to flow through. Series ● In a series circuit, the electrical components share a current flow and have common nodes. ● In a parallel circuit, the electrical current splits paths and comes back to the negative terminal of the power source. vs. Parallel ❏ Kirchhoff’s Laws ❏ German physicist who created laws to calculate currents, voltages, and more also extended the theory of Georg Ohm Kirchhoff’s Current Law (KCL) ❏ ❏ ❏ ❏ the sum of all currents entering a node is equal to the sum of those leaving based on conservation of charge also referred to as the junction rule can be used to solve for I, V, and R in a circuit with unknown quantities Kirchhoff’s Voltage Law (KVL) ❏ ❏ ❏ ❏ ❏ the sum of all voltage changes around a complete path is equal to 0 based on the conservation of energy similar to displacement can be used to solve for I, V, and R in a circuit with unknown quantities also referred to as the loop rule What do you call a detective electrician? M re About Circuits Sherlock Ohms! A short circuit is when you connect a wire directly from the positive end to the negative end of the power supply. DO NOT DO THIS! This can cause explosions. What is a Short Circuit? Circuits and Our Lives What did the baby light bulb say to the momma light bulb? Circuits are incorporated into our lives in many ways. They are used in nearly every type of item that uses electricity, from a phone to a lamp. I love you watts and watts! Example of a Circuit Another Example of a Circuit Another example of a circuit is a device I built with a few of my classmates at school for a competition. It will alert the guardian of an child if it is too hot inside the car for the child via a buzzer and LED lights. This device uses a pressure sensor, a temperature sensor, and the alert system. It uses a battery as the power source.