Series and Parallel Circuits - PowerPoint Presentation

Slide1

Series and Parallel CircuitsSlide2

Electric Power

How was power define before?

Time rate of doing work or using energy

Electric Power - Rate at converting electrical energy into other forms of energy.

P = W/t or P = E/t

Unit: watt, w = J/s

60w light bulb converts 20 J of electric energy to light and heat each second. Slide3

P =

E

t

V =

E

Q

E = Q V

P =

Q V

t

P = I VSlide4

Example

What is the resistance of a 1200w electric frying pan that draws a current of 11a?

9.9 ΩSlide5

Problem Set 1

1. An appliance draws 13 a when connected to a 110v circuit.

a. What is the power of the appliance?

b. What is its resistance?

2. What is the power of a light bulb that has

a resistance of 190 in a 120 v circuit?Slide6

What does the power plant sell you? Slide7

Problem Set 2If the local power company charges $0.080/kw * h, how much (to the nearest cent) will it cost to use:a 75 W CD player for 5.0 hours?

a 2.3

kw

oven for 45 minutes?

a TV drawing 2.0 amps of current in a 120 v circuit for 3.5 hours?Slide8

Series Circuits

Resistors are connected in a single path. Slide9

Parallel Circuits

Resistors are connected in separate branches.

There is more than one path for current. Slide10

Series Circuit Lab

Make the following circuit. Remember an ammeter goes into the circuit as shown in the diagram.

ASlide11

Now add a second resistor in the circuit, as shown in the diagram below.

Observe the brightness of the bulbs.

ASlide12

Now, add a third resistor into the circuit, as shown in the diagram below.

Observe the brightness of the bulbs.

Remove one of the bulbs and record the results.

ASlide13

Part B

Construct the following diagram with the ammeter at the A

T

location.

Next, move the ammeter to the A

1

and A

2

sites and record the current. Slide14

Part C

Place the

Multimeter

in the voltage terminal and switch the dial to Voltage setting.

Build the following circuit and place the voltmeter on either side of the battery at the V

T

. Remember a voltmeter is connected around the battery or resistor since it measure a difference in potential energy between two locations.

Now move the voltmeter to V

1

and V

2

locations. Slide15

Parallel Circuits Lab

Place the

multimeter

back in the ammeter setting by switching to terminals and the dial setting to A.

Construct the circuit depicted in the diagram below.

Observe the brightness and the current and record your observations.

ASlide16

Add a second resistor in parallel as depicted in the diagram below.

Observe the brightness of the light bulbs and the current and record your observations.

ASlide17

Add a third bulb in parallel. Make observations and record.

Unscrew a bulb and make observations. Record

Answer conclusion questions.

ASlide18

Part B

Remove one of bulbs in the circuit and keep the ammeter in the same position A

T

.

Now, move the ammeter to the other two sites to measure the current in different paths. Slide19

Part C

Switch the

multimeter

to the voltmeter setting by moving the terminals and turning the dial to the voltage setting.

Place the voltmeter in parallel with the battery by reading the V

T

, terminal voltage.

Move the voltmeter to the other two locations, V

1 and V2. Slide20

Conclusions

Use ohm's law to calculate the resistance in the different positions.

Answer the Conclusions. Slide21

Series Circuits

Current is

the same

in all parts of the circuit

I

t = I

1 = I2 = ...Slide22

Series Circuit

Voltage drops across resistors adds up to the total voltage provided by the battery.

Energy is conserved.

V

t

= V

1 + V2 + V3Slide23

Series Circuits

Total resistance is found by adding the resistance of each device.

R

t

= R

1

+ R2 + R3Slide24

RT _____ VT _____ IT

_____

V

1

_____

V

2 _____ V3 ____

R

1

= 15Ω

R3 = 5Ω

R2 = 20Ω

80vSlide25

Video Problem Set 3Slide26

Problem Set 4Slide27

What would happen if your house was wired in series circuits?

What would happen as you added more and more things to the circuit?

What would happen if one appliance malfunctioned? Slide28

Current in Parallel Circuits

4a

2a

2aSlide29

Current in Parallel Circuits

Current in each branch

adds up

to the total current of the circuit.

Electric charge is conserved

4a

1a

3aSlide30

Current in Parallel Circuits

Current in each branch

adds up

to the total current of the circuit.

Electric charge is conserved.

I

T

= I

1

+ I

2

+ I

3 + …Slide31

Voltage in Parallel Circuits

6v

6v

6vSlide32

Voltage in Parallel Circuits

Voltage drops across resistors in each branch

equals

total voltage provided by the battery.

V

T

= V

1

= V

2

= V

3 = …Slide33

Resistance in Parallel Circuits

Equivalent resistance is less than resistance of each resistor alone.

1 1 1 1

R

eq

R

1

R

2

R

3

=

+

+

+

…Slide34

Examples

What is the equivalent resistance of:

Two 10Ω resistors in parallel?

5Ω

Two 8Ω resistors in parallel?

4Ω

Three 9Ω resistors in parallel?

3Ω

A 60Ω, a 30Ω , and a 20Ω resistor connected in parallel?

10ΩSlide35

Problem Set 1Slide36
Slide37

Equivalent Resistance

The two resistors in parallel can be replaced with a single resistorSlide38

ExampleSlide39

Problem Set 2Slide40

Problem Set 3Slide41

In which type of circuit is there only one path for the charges to travel?

In a series circuit, the voltage drops across the resistors,

Equals the voltage of the battery

Adds up to the voltage of the battery

Is less than the voltage provided by the battery

When resistors are connected in ______, voltage stays the same in all branches.

The term equivalent resistance is used for resistors connected in _____.

Our homes are wired in ______.