In this lesson, we will learn:
- A brief review on voltage, current, and resistance
- Establishing 4 main concepts for problem solving:
- Concept #1: a smaller resistor uses up less voltage; a bigger resistor uses up more voltage
- Concept #2: the more resistors added in series with the battery into the circuit will increase the total equivalent resistance
- Concept #3: the more resistors added in parallel with the circuit will decrease the total equivalent resistance
- Concept #4: the brightness of a lightbulb is related to the voltage drop across it (as well as the power dissipated by it)
- Solving questions for more conceptual electric circuits questions:
- Using a combination of all previous concepts and formulas ( Ohm’s Law, , Power)
- As well as applying the 4 main concepts
Notes:
- Before facing problem solving questions for electric circuits that are oftentimes just as conceptual as they are mathematical, one must have a firm understanding of the concepts of each lesson thus far:
- Voltage: staircase analogy, Kirchhoff’s Loop Rule, equal voltage in parallel
- Current: water analogy, Kirchhoff’s Junction Rule
- Resistance: calculating total resistance for series vs. parallel configurations
- The conceptual relationships as defined by Ohm’s Law:
- The shortcut for Ohm’s law; the voltage divider method:
- The concept of terminal voltage and calculations:
- Power: total power is additive, and
- Energy: and
- The 4 main concepts can be summarized as follows:
- I. The greater the resistance of a resistor, the more voltage that it uses up (and vice versa; a smaller resistor uses less voltage)
- II. The more resistors added in series, the greater the equivalent resistance
- III. The more resistors added in parallel, the lesser the equivalent resistance
- IV. The brightness of a lightbulb is related to the voltage it uses up (its voltage drop) as well as, the power dissipated by it
- The brightness of a lightbulb is related to the amount of voltage that it uses up (voltage drop); the more voltage used, the brighter the light bulb
- The voltage drop is dependent on current and resistance ()
- The brightness of a lightbulb can also be understood as how hot the filament is burning
- The incandescent lightbulb is transforming electrical energy into thermal and light energy; the rate of energy transformation is power
- Power is dependent on voltage () as well as current and resistance ( )
- When observing lightbulbs in series:
- Adding more lightbulbs in series will increase the overall resistance, thus diminishing the total current—this leads to a smaller voltage drop across each lightbulb, causing a dimming effect
- Opening a switch or having a single broken lightbulb in the series chain will cause all relevant lightbulbs turn off (the whole circuit will be compromised)
- When observing lightbulbs in parallel:
- Adding more lightbulbs in parallel will decrease the overall resistance, thus increasing the total current—the balance leads to relatively constant brightness across all parallel lightbulbs
- Opening a switch or having a single broken lightbulb will not compromise the whole circuit; only the relevant branch of the circuit will be affected (turned off)