Voltage  Electric Circuits
Voltage
Lessons
Notes:
In this lesson, we will learn:
 What is an electric circuit and what are the main components: battery (voltage), closed wire path (current), and devices/resistors that use up electricity (resistance)?
 How to draw a schematic diagram using simplified symbols to represent a circuit.
 How to tell the difference between series vs. parallel configurations for resistors in a circuit.
 What is a battery and how does it provide voltage for an electric circuit?
 What is voltage?
 Kirchhoff’s 2^{nd} Rule: Loop Rule for solving voltage questions
 Voltage in parallel rule: the voltage used in parallel settings are EQUAL
Notes:
 An electric circuit is a closed loop that electric charge flows within; circuits contain 3 main components:
 (1) a source of electrical energy (battery)
 (2) a complete pathway for electric charges to flow through (wire), and
 (3) one or more devices that use up electricity (electronics, resistors).
 A schematic diagram is a simplified drawing of an electric circuit which uses universal symbols for each component of an electric circuit. A battery’s (+) positive terminal is drawn as a longer line whereas its () negative terminal is drawn as a shorter line.
 The conventional current is the flow of positive charge, starting from the battery’s (+) positive terminal, travelling through the entire circuit, and ending at the () negative terminal.
 An electric circuit’s attached electronic devices (lightbulbs or resistors) can be connected in either series or parallel configurations.
 Series: resistors are connected in series if they are in a single and continuous path
 Parallel: resistors are connected in parallel if they are in multiple, branching paths
 A battery provides voltage to an electric circuit; it drives the electricity throughout the circuit.
 A battery converts chemical energy into electrical energy; the reductionoxidation reaction that occurs within the battery generates excess free energy which is put into the circuit as electrical energy.
 Voltage is a type of electrical potential difference. The voltage of a battery represents how much energy it can provide the circuit; voltage can also represent how much energy is lost/used across resistors/devices (“voltage drop”).
 The unit for voltage is Volts (V) (which is equivalent to Joule/Coulomb or energy per charge). It is a scalar quantity.
 Kirchhoff’s 2^{nd} Rule, also known as the Loop Rule, states that the sum of charges in electric potential (voltage) around the circuit (closed path) will be equal to zero.
 In other words, all the voltage stored in the battery will be used up by the devices (resistors) in the circuit; the magnitude of battery voltage is equal to the sum of all voltage drops across resistors in the circuit.
 Voltage in parallel configurations have a special rule: the voltage used in parallel settings are EQUAL (each parallel branch will have the same amount of voltage drop).
 We will use the stair case analogy for voltage (going down stairs in a building).
 Starting with the battery voltage (at the positive terminal) as the top floor, and going down a number of floors at each resistor (voltage drop), until you get to floor zero (end at the negative terminal)

Intro Lesson

4.
Finding Voltage across Resistors and at Certain Points in More Complex Circuits