Download Note Guide Ohm`s Law, Power and Electrical Energy

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Note Guide Ohm’s Law, Power and Electrical Energy
Slide 1 – Voltage (Potential Difference)
1. Voltage measures __________________________. Measure of ____________ ___________
2. Unit for voltage is ________ (__)
3. “Potential difference” flows from ____________ energy to ______________ energy.
4. The potential difference of the battery is _______________.
5. The higher the energy, the greater the ____________ (________________ ___________).
Slide 2 – Current
6. Current is the ____________ of flow of an ____________ ______________.
7. The unit for current (__) is ________________ or ________ or (__).
8. How does the faucet help you understand the concept of electrical current?
Slide 3 –Resistance
9. Resistance-the ___________________ or _____________ the flow of current.
10. The unit for resistance is ________.
11. Draw the symbol:
Slide 4 – Review of Resistance, Current, and Voltage
12. Match the word on the left to the phrase on the right.
_______Resistance (R)
How fast?
_______Current (I)
How much?
_______Voltage (V)
How much is it slowed down?
Slide 5 Electrical Measuring Instruments
13. __________________-used in parallel to measure voltage
14. __________________-used in series to measure current
15. ______________________-used to detect a current
16. _____________________-measures resistance
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Slide 6-7 – Ohm’s Law
17. State Ohm’s law using symbols.
Georg Simon Ohm
18. If voltage goes _______, the charges move a little faster between atoms and we get ______ current.
19. A current vs. voltage graph shows us if resistance _____________.
20. Resistance of metals ______________ with temperature, because the particles ____________
______________ often causing more resistance.
Slide 8 Calculating Ohm’s Law
So, to find Current, we need to
DIVIDE voltage by resistance
And, to find Resistance, we need to
DIVIDE voltage by current.
Slide 9-10 – Calculate Ohm’s Law
21. Calculate the potential difference (voltage) across a 3 ohm resistor if a 0.5 amp current
flowing through it.
I=
Formula
Substitute
Answer
V=
R=
2
22. A radio with a resistance of 240 ohms is plugged into a 120 V outlet. What is the current
flowing from the outlet?
I=
Formula
Substitute
Answer
V=
R=
Slide 11- Practice
How many ohms of resistance must be present in a circuit that has 120 volts and a current flow equal
to 10 amps?
I=
Formula
Substitute
Answer
V=
R=
Slide 12 – Power
23. Is the rate at which ___________ _________.The unit for power (
) is _____________.
24. State the formula for solving power problems:
So, to find Current, we need to
DIVIDE power by voltage
And, to find Voltage, we need to
DIVIDE power by current.
Slide 13 where do power units come from:
Watts =
____________
Joules
second
=
___________ X _______________
Joules
Coulomb
Coulomb
second
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Slide 14 Electrical Power Problem
If CD player uses 4.5 V with 0.2 amps of current, what is the power that it uses?
P=
Formula
Substitute
Answer
I=
V=
Slide 15
A toaster uses 950 W on a 120 volt circuit. What is the current?
P=
Formula
Substitute
Answer
I=
V=
Slide 16 – Electrical Energy
25. The unit for electrical energy is _________________________.
26. The formula for calculating electrical energy is
So, to find Power, we need to
DIVIDE energy by time.
And, to find time, we need to
DIVIDE energy by power.
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Slide 17-18 Electrical Energy Problem
1. You use your hairdryer for 10 minutes every day. The hairdryer uses 1000 W. How many
kilowatt-hours does your hairdryer use in 12 days?
E=
Formula
Substitute
Answer
P=
T=
2. A refrigerator operates at 3.5 kW of power. It runs for 18 hours per day. How many kilowatt-hours of
energy are used per day?
E=
Formula
Substitute
Answer
P=
T=
3. You use your 60-W DVD player to watch your favorite movie. If the player uses 0.17 kWhr of energy
while playing the film, what is the running time of the movie? (Watch your UNITS)
E=
Formula
Substitute
Answer
P=
T=
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