Download Unit 5: Electricity

7.6 - Series and Parallel Circuits
Batteries in Series
• Positive terminal is connected to the
negative terminal of the next battery and so
on.
• Increases the amount of voltage.
• Typical electrical cell is 1.5 V
• Example: If you connect 3 cells, the
voltage becomes 4.5 V.
• The electrons get three boosts of energy
instead of one.
Batteries in Parallel
• All of the positive terminals of the cells are
connected and all of the negative terminals are
connected.
• Voltage stays the same.
• Amount of electrical charge increases.
• Example: Connecting two cells in parallel
means there will be twice as many electrons
available.
• So, a bulb will glow twice as long.
Kirchhoff’s Rules
• Kirchhoff’s Current Rule (KCR)
• At any junction point:
• the total current into the junction equals the
total current out of the junction.
• Kirchhoff’s Voltage Rule (KVR)
• In any complete path:
• the sum of the voltage rises equals the
sum of the voltage drops.
Sample problem 1
Problem 2
Resistors in Series
• For any number n of resistors
connected in series, the equivalent
resistance is
• Rt = R1 + R2 + ... Rn
• Recall  R=IV
Sample problem 3
Resistors in Parallel
• For any number n of resistors
connected in parallel, the equivalent
resistance is found by using the
equation
Sample problem 4
• Calculate the equivalent resistance of a circuit
with the following resistors in parallel: 5, 10, and
30 ohms.
• *** SAMPLE PROBLEM 5 - For the circuit shown
below, determine both the current through and the
potential drop across each resistor.
HOMEWORK
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P.337 #1-3
P.339 #4-5
P.340 #7
P.342 #9