Chapter 20. Foundations of Physics. Electricity and Magnetism. Electric Circuits and Power. 20 Series and Parallel Circuits 20 Analysis of Circuits 20 Electric Power, AC, and DC Electricity. Objectives. Recognize and sketch examples of series and parallel circuits.
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Foundations of Physics
Electric Circuits and Power
a. Battery f. Fixed resistor
b. Light bulb g. Capacitor
c. Motor h. Buzzer
d. Switch i. Ammeter
e. Variable resistor
2. Define a series circuit
3. Show the formula depicting five resistors in a series circuit
4. Describe Ohm’s Law
5. Draw and Calculate the total resistance in a series circuit containing two 1.5 ohm light bulbs, a battery, a 1 ohm buzzer, a switch, and a 5 ohm motor
Rtotal = R1 + R2 + R3...
Individual resistances (W)
As current flows along a series circuit, each type of resistor transforms some of the electrical energy into another form of energy
Ohm’s law is used to calculate the voltage drop across each resistor.Voltage in a series circuit
If three 1.5 ohm light bulbs are wired in series what necessary voltage would be required to push .5amps of current through the circuit?
17. Describe a short circuit
Parallel circuits have two big advantages over series circuits:
1. Each device in the circuit sees the full battery voltage.
2. Each device in the circuit may be turned off independently without stopping the current flowing to other devices in the circuit.
Calculate the total current supplied by the battery.18. Calculate current
19. Describe the resistance in a parallel circuit
20. Write the formula for calculating total resistance in a parallel circuit
Calculate the total resistance of the circuit.Adding resistance in parallel circuits
The bulb requires 1 amp of current.
If the bulb were connected directly to the battery, it would draw 6 amps and burn out instantly.
To limit the current, a resistor is added in series with the bulb.
What size resistor is needed to make the current 1 amp?Solving circuit problems
Three volts are applied to the circuit.
Calculate the current in each of the bulbs.
26.From your calculations, do you think all three bulbs will be equally bright?Calculate using network circuits
28. How is power calculated?
29. What is the unit for power?
30. Describe a kilowatt
31. Describe horsepower
P = VI
Calculate the power used by the light bulb.32. Calculate power
How much does it cost to use the coffee maker one hour per day for a month?33. Calculate power
35. Define alternating current
36. What is meant by 60Hz alternating current?
Because motors store energy and act like generators, the current and voltage are not in phase with each other.
The current is always a little behind the voltage.Power in AC circuits
Avg. current (amps)
P = VI x pf