Chapter 32 #1-16

When drawing circuits, schemes, you must use the accepted symbols for : Battery Wire Resistor Bulb Junction Capacitor Switch

Circuit analysis is based on Σ Iin=Σ Iout A charge that moves around a looped circuit/path and returns to the starting point has a change in potential of zero. This idea implies that somewhere in the circuit there is a combination of positive and negative potentials.

Hints: As you go through each circuit element, a change in potential difference (ΔV) is interpreted as: For an ideal battery, current traveling from negative to positive, potential increases (ΔV = +ε) For an ideal battery, current traveling from positive to negative, potential decreases (ΔV = -ε) For a resistor, current traveling from positive to negative, potential decreases (ΔV = -IR)

Example: Lets look at #4 and #43 from pages 992 and 994!!

Remember the work kinetic theorem allows us to convert a mass’ motion into work. Therefore, 1/2mv2 = W = qEd = ΔEtherm And thermal energy depends on the charge through a resistor qΔVR

Power in a resistor is equal to the result of current and potential difference of the resistor. Ultimately this relationship is PR= I2R= I(ΔVR) Thermal energy dissipated(lost) is the result of time and the power of the resistor (PRt= Etherm)

Example #8 from page 993 and #26 from the guided reading:

When you buy a battery you are actually purchasing potential. Real batteries have internal resistance which add to the resistance of the circuit I=ε/(R+r)

The batteries internal resistance causes the battery to loose % potential difference compared to an ideal battery which has no internal resistance.

Example: Compared to an ideal battery, by what percentage does the battery’s internal resistance reduce the potential difference across the 20Ω resistor? (see diagram on board)

A battery will “short” if the maximum possible current on the circuit is exceeded. Short circuit current is found by Isc =ε/r Shorting out a battery is EXTREMELY dangerous!!!

Resistors in parallel… Have equal potential difference but different current. Rp = (1/R1 + 1/R2 + 1/R3 +…)-1 Current is still found through I = ε/ΣRp

Example #22 and 24 from page 993

Mixing resistors in series and parallel takes a bit more thinking/planning: 1.Reduce circuit to the smallest combination of resistace to calculate ΣR so that you can calculate I through the circuit. 2.Work “back” through reduced schematic to solve for ΔV and I in each component. 3.Use table format to summarize calculations.

Example #61 from page 996: