Plan for Today (AP Physics I)

• Inquiry questions on circuits• Lecture on Series and Parallel Circuits

Parallel and Series Circuits

Parallel Series

Instructions

• Create a series and parallel circuit with three capacitors and charge them with 6 V

• Measure the voltage across each capacitor• Discharge the circuit with a light bulb noting

the length of time.• Sketch your set up and label the voltages• Describe the differences between the two

circuits (include V and q)

Series and Parallel Circuits

Series Circuit

• Single path around• Steps– 1. An electron is pushed out of

the negative end of the battery and deposited on the 1st plate

– This pushes an electron off the opposite plate on to the next plate

– This repeats with the next capacitor down the line until one electron reaches the battery

– The whole process repeats until the energy of the battery (voltage) is completely used

In a series circuit

• What is the same?• q for each the same

• What is different?• voltage

• Energy of the battery is spread out over all the capacitors

Series Circuits

• We would like to collapse capacitors down to one equivalent capacitor

• It would help us solve for values

• Ceq is what the 3 capacitors in series act like• So what is the same?• q on each

• qeq = q1 = q2 = q3

• VB = V1 + V2 + V3– Because voltage is distributed across

• C = q/V• So V = q/C – can sub in

• But all the q’s are the same

• Series Circuit equation

Example

• Solve the following circuit. Find q1, q2, q3 and v1, v2, and v3.

Parallel Circuit

• Has multiple paths

Parallel Circuits

Diagram Flow of electrons• 1. Look at C1 first. An

electron is pulled off and deposited until all the energy of the battery is used

• 2. This repeats with the 2nd and 3rd capacitors.

• What is the same for each capacitor?

• Voltage

Parallel Circuits

Parallel Circuits - Calculations

Example Problem – Parallel Circuits

• Analyze the following circuit and find V1, V2, and V3 and q1, q2, and q3.

Example Problem – Parallel Circuits

• Analyze the following circuit and find V1, V2, and V3 and q1, q2, and q3.