1. Direct and Alternating Current

2. Direct and Alternating Current
Direct Current (DC) -
Current that flows in only one direction through a wire
Ex: a battery

3. Alternating Current (AC) -
Reverses the direction of the current flow in regular patterns
Ex: a plugging a toaster into an outlet

4. ELECTRIC CIRCUITS
6.3

5. ELECTRIC CIRCUITS Complete path through which charge can flow.
Switches can be opened to allow electricity to flow or closed.

6. Copy these electric circuit symbols into your notebook
Copy these electric circuit symbols into your notebook. Use these symbols when drawing your circuits.

7. TYPES OF CIRCUITS
Series Circuit – charge has ONLY ONE way to flow (direct current)
If one element stops working they all stop
EX: Flashlight, car, holiday lights

9. Parallel Circuit – charge can flow through TWO or MORE pathways (alternating current).
If one element stops functioning the rest will still operate
EX: House

10. Complex Circuits
A circuit composed of both series and parallel circuits

11. ELECTRICAL SAFETY
Electrical energy enters your home at the circuit breaker or fuse box and branches out to appliances, wall sockets, and lights.

12. ELECTRICAL SAFETY
Fuse – prevents current overload in a circuit by melting
Circuit Breaker –switch that opens when the current in a circuit is too high
Grounding – transfer of excess charge through a conductor to Earth

13. P = I × V Electrical Power
rate at which electrical energy is converted to another form of energy
SI unit for electrical power is Watt (w)
P = I × V
P - power (W)
I - current (A)
V- potential difference (V)

14. V P I P = I · V I = 0.01 A P = (0.01 A) (9 V) V = 9 V P = 0.09 W P = ?
A calculator has a 0.01 A current flowing through it. It operates with a potential difference of 9 V. How much power does it use?
WORK:
P = I · V
P = (0.01 A) (9 V)
P = 0.09 W
GIVEN:
I = 0.01 A
V = 9 V
P = ? P I V

15. V P I P = I · V I = 10 A P = (10 A) (120 V) V = 120 V P = 1,200 W
PRACTICE Problems
16. A toaster oven is plugged into an outlet where the voltage difference is 120 V. How much power does the toaster oven use if the current in the oven is 10 A?
WORK:
P = I · V
P = (10 A) (120 V)
P = 1,200 W
GIVEN:
I = 10 A
V = 120 V
P = ? P I V

16. V I = 0.05 A P I I = P/V I = ? I = 6.0 W / 120 V V = 120 V P = 6.0 W
PRACTICE Problems
17. A video-disc player that is not playing still uses 6.0 W of power. What is the current into the video-disc player if it is plugged into a standard 120-V outlet?
WORK:
I = P/V
I = 6.0 W / 120 V
I = 0.05 A
GIVEN:
I = ?
V = 120 V
P = 6.0 W P I V

17. PRACTICE Problems
17. A video-disc player that is not playing still uses 6.0 W of power. What is the current into the video-disc player if it is plugged into a standard 120-V outlet?
0.05 A

18. PRACTICE Problems
18. A flashlight bulb uses 2.4 W of power when the current in the bulb is 0.8 A. What is the voltage difference supplied by the batteries?
3 V

19. E = P × t Electrical Energy
energy use of an appliance depends on power required and time used
E = P × t
E - energy (kWh)
P - power (kW)
t - time (h)

20. t GIVEN: P = 700 W = 0.7 kW t = 10 h E = ? WORK: E = P · t
A refrigerator is a major user of electrical power. If it uses 700 W and runs 10 hours each day, how much energy (in kWh) is used in one day?
GIVEN:
P = 700 W = 0.7 kW
t = 10 h
E = ?
WORK:
E = P · t
E = (0.7 kW) (10 h)
E = 7 kWh E P t

21. PRACTICE Problems
21. A TV with a power rating of 200 W uses 0.8 kWh of electrical energy in one day. For how many hours was the TV on during this day?
4 hours

22. PRACTICE Problems
22. A hair dryer has a power of 1,200 W. How much electrical energy does the hair dryer use in 3 minutes?
0.06 kWh

23. Electric Circuits Review
What is a series circuit?
What is an example of a series circuit?
What is a parallel circuit?
What is an example of a parallel circuit?
What is the Scientific Unit for electrical power?
What is the definition of electrical power?
What is a circuit breaker?
What does a fuse prevent?
What is grounding?
What is the Scientific Unit for electric current?