Resistors in Series and Parallel
Ch.10.5 pg 320-325
Welcome back!
• Please pick up your name plate
• Please pick up three handouts from the front:
– Resistors in Series and Parallel
– Problems with circuits with resistors
– Current Voltage Resistance Review
Agenda
Goal: Given a circuit, calculate
- current (may change from resistor to resistor in parallel; remains the same in
series)
- voltage (may change from resistor to resistor in series; remains the same in
parallel)
- total resistance (increases with the number of resistors in series; decreases
in parallel)
1. Questions about Ohm’s Law Lab
2. Notes: Resistors in Series and Parallel
3. Work on homework: Problems with circuits with
resistors
4. Introduction and Co-creating cell phone rules
Important dates
• Please take out your agenda write down these
dates:
1. Current Electricity Unit Test is on:
Feb 13th / Feb 16th
2. Ohm’s Law Lab is due on:
section 1-2 on Feb 12th
section 2-2 on Feb 13th
3. If you missed Ohm’s Law Lab, make-up lab is on
Wednesday, February 11th, during lunch in
W204
Questions about Ohm’s Law Lab
• Please take out Ohm’s Law Lab task sheet
Notes: Resistors in Series and Parallel
1. Series Resistors: In a series circuit the same current is
applied across each resistor but the voltage divides at
each resistor.
IT = I1 = I2 = I3
VT = V1 + V2 + V3
RT = R1 + R2 + R3
The total resistance in a series circuit is equal to the sum
of the individual resistances
Notes: Resistors in Series and Parallel
1. Parallel Resistors: In a parallel circuit, the voltage applied
across each resistor is the same, but the current divides at
each resistor.
IT = I1 + I2 + I3
VT = V1 = V2 = V3
1
RT
=
1
R1
+
1
R2
+
1
R3
The sum of the reciprocals of the resistances in a parallel
circuit equals the reciprocal of the total resistance in the
circuit RT
Summary Table
Type of Circuit
Series Circuit
Parallel Circuit
Total current (IT)
IT = I1 = I2 = I3
IT = I1 + I2 + I3
Total voltage (VT)
VT = V1 + V2 + V3
VT = V1 = V2 = V3
Total resistance (RT)
RT = R1 + R2 + R3
1
RT
=
1
1
+
R1 R2
+
1
R3
Homework
• Worksheet: “Problems with circuits with
resistors”
• After you are finished with worksheet and
checked your answer, please work on
“CURRENT VOLTAGE RESISTANCE REVIEW”
A few announcements
• Handout: introductions (if you don’t have one)
• When you come into class – Please read the instructions on
powerpoint / whiteboards
• For your safety, please report to me when you come in late
• When I ask for your attention, I want to see:
– Your eyes on me
– Your hands free
– Your lips sealed
• Washrooms: one person at a time, if possible
– write your name in the corner of whiteboard
when you leave. Erase your name when you
return
• Where to find handouts
• During labs: please put away your binders and
bags under the tables on the sides
Electronic Devices Contract
• Please get into groups of 4-5
• On a large white paper, write down:
– Your names
– Make rules around using cell phones and
electronic devices in class
– Consequences for keeping and breaking the
“contract”