6.5 Energy & Power in a circuit

• Natuurkunde / Scheikunde
• Middelbare school
• vmbo b, k, t, havo, vwo
• Leerjaar 1-3

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6.5 

Today

• Homework: Questions
  
  
• Energy & Power in a circuit

Learning objectives

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

Questions about the homework?

Homework was:

 42, 43, 44 page 188

What is energy?

What is energy?

Hard to say!

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

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

Tell me what energy goes in and out

• chemical ce. to kinetic e.
• kinetic e. to electrical e.
• electrical e. to radiation e. and heat
• chemical e. to radiotion e. and heat
• radiation e. to electrical energy
• nuclear e. to electrical e.
• electrical e. to movement and sound and light
• electrical e. to chemical e.
• chemical e. to kinetic e. and heat
• chemical to heat
• radiation e. to chemical e.
• electrical e. to heat
• electrical e. to gravitational e.

• a driving car
• a rotating windmill
• a burning lamp
• a burning candle
• a working solar panel
• a working nuclear powerplant
• a smartphone that is being used
• a smartphone that is being charged
• someone riding a bike
• your body when it is not moving
• a tree that catches the sunlight
• a boiler cooking water
• an elevator lifting people

Tell me what energy goes in and out

• a driving car
• a rotating windmill
• a burning lamp
• a burning candle
• a working solar panel
• a working nuclear powerplant
• a smartphone that is being used
• a smartphone that is being charged
• someone riding a bike
• your body when it is not moving
• a tree that catches the sunlight
• a boiler cooking water
• an elevator lifting people

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

                                           E in Joule = P in Watt * ∆t in second

                                                            

                                                                    P in Watt = J/s             

                                  

Everybody try it now! 

How many Joule are used when:

I have an airfryer of 2500 W which is on for 600 s?

I have a lamp of 20 W which is on for one whole day?

E=P⋅Δt

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

                                           E in Joule = P in Watt * ∆t in second

                                                            

                                                                    P in Watt = J/s             

                                  

Everybody try it now! 

How many Joule are used when:

I have an airfryer of 2500 W which is on for 600 s?   2500W*600s = 1.500.000 J = 1,5 MJ

I have a lamp of 20 W which is on for one day?        20W*24*60*60s = 1.728.000 = 1,7MJ

E=P⋅Δt

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

Joule is very small. More convenient is the kWh = kiloWatt * hour

1 kWh = 3.600.000 J = 3,6 MJ
                                                                convert:

                                                            J       --> kWh -->  : 3.600.000

                                                            kWh --> J       --> x 3.600.000

                                                            

                                                                    P in Watt = J/s             

                                  

E=P⋅Δt

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​​

Making excercises

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

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

                                   

until: 13:45 

Exchange:
The following person may explain:

V5

V2

Check the answers

exercises

 33 & 40 page 183/184