6.5 Energy & Power in a circuit - part 2

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6.5 

Today

• Three quiz questions about energy & power
  
  
• Homework: Questions
  
  
• Energy & Power in a circuit: Calculate based on current & voltage

Learning objectives

• You can calculate the power  and energy a circuit is using from the current and the voltage.

What does power mean?

1. Watt.
2. Power is another word for Force.
3. Energie, so unit is J.
4. Energy per time, so unit is J / s.

If I have a game pc that uses
350 W of power.
How much energy does it use in 1 h?

1. 1.260.000 J = 1,26 MJ
2. 350 J
3. 21.000 J = 21 kJ
4. 0,350 J

What is energy?

Name some properties

• Cannot be made
• Cannot be destroyed
• Can transform into another type
• Is needed for any physical proces to run
• All physical processes transform energy

Questions about the homework?

Homework was:

56, 57, 58, 59, 60 page 193

Two ways to do 59.
0,4 kW lawn mower used for 5 h.

What can we derive about how Power relates to Current and Voltage?

What do we know from the book?                          What do we know from the video:

U = voltage

I = current 

                                                            

                                                                    P in Watt = J/s             

                                  

E=P⋅Δt

P=​Δt​​E​​

I=​Δt​​Q​​

U=​Q​​E​​

Group maker in SOM

You're done as a collective when:

• Everybody in the group understands
   the solutions.
• Everybody in the group has written a   structured solution in their notebook.

Watching TV

I have a tv that consumes a current of I = 0,5 A.

(voltage is the standard voltage of an outlet!)

How much power does it use?     ( P in Watt=J/s )

How much energy does it use if I watch tv for 2 hours?  

 

E=P⋅Δt

P=​Δt​​E​​

E=U⋅Q

P=U⋅I

Equations I know now: 
                                                        

Relation of power and energy:                                               energy used = power * time interval

How energy relates to voltage:                                               energy a charge gets = voltage*charge

How power relates to voltage                                                 power = voltage * current

                                    and current:                                     

Making tea

I have a water boiler that uses a current of I = 6,5 A.

My energy company charges me €0,30 per kWh

What do I have to pay a week, if I use it for 30 minutes 
each day.

 

1 kWh = 3,6 MJ = 3.600.000 J

Making excercises

Try it yourself, and feel free to consult your neighbour.

Do exercises
 56, 57, 58, 59, 60  page 193

                                   

until:14:05 

Name some types of energy

• Electrical energy
• Kinetic energy = Energy of motion
• Chemical energy (petrol, sugar, ...)
• Gravitational energy
• Wind energy
• Radiotion energy (for instance solar energy)
• Heat

the quantity of Energy is expressed in the unit of Joule

the quantity of Power is expressed in the unit of Watt

together:

                                           energy used = power * duration it is on

                                                            

                                                                    P in Watt = J/s             

                                  

Energie in kWh = vermogen in kW * tijd in uur

         

E=P⋅Δt

E​kWh​​=P​kW​​⋅t​h​​

Exchange:
The following person may explain:

V5

V2

Check the answers

exercises

 33 & 40 page 183/184