DC Circuits

Prof Mason provided an example of a DC circuit board. When the switch is turned on the lower bulb and upper bulb stay the same. The components are in parallel with one another.

This is a schematic of the DC circuit board.

Bulbs and batteries in relation to components being in series or parallel to each other:

In a series circuit, the voltage is additive.

Current in a parallel circuit is additive.

Below we used the given diagram to find the total resistance. The formulas for resistances in series and parallel is shown in red below. We first had to simplify the schematic. We found the resistance of box one and three. Then we solved for resistance of box two by using the simplified resistances from box one and three. 

When measuring voltage, we must always measure across an element. The voltage of the source is proportional to the voltage of the bulbs. The voltage in a series circuit is additive.

For current, we measure through an element. The voltage and current are proportional to one another. The current in a series circuit is the same at all points.

In parallel circuits, the voltage is the same at each point.

In parallel circuits, the current is additive.

 Here is a resistor connected in series.

Next, we used the following chart to compare our measurements of 4 resistors to accepted values.

The accepted values are on the left and the measured values are on the right. We used a multimeter and took down values for resistance. Each of the resistors had colored bands on them which allowed us to compared them to the chart above. All of our measurements fall within the accepted resistances.  

Summary:

• In series circuits:
• voltage is additive
• current is the same throughout the circuit
• resistance is additive
• In parallel circuits:
• voltage is the same throughout the circuit
• current is additive
• resistance is found using the formula: 1/Re=(1/R1) + (1/R2) +...(1/Rn)
• We can simplify schematics to solve for total resistance in a circuit when using the rules above.
• When measuring voltage, we must always measure across an element.
• For current, we measure through an element. The voltage and current are proportional to one another. 
• Resistors used in this lab were all marked by bands indicating the accepted resistances with uncertainty.