2 YR2_T2_LSN5 2.3

• Science
• Middelbare school
• havo, vwo
• Leerjaar 2

YR2_T2_LSN5

Topic 2.3 Electricity

Planning for today

• Topic 2.3 Electricity

Learning goals 2.3

I can…

• Explain what electrical energy is made of.
• Explain what current is, along with its unit of measurement.
• Explain what voltage is, along with its unit of measurement.

Key words

Electricity

Electrons

Electrical current (I)

Ampères (A)

Voltage (U)

Volts (V)

Voltage source

Power (P)

Watt (W)

Energy

What is electricity?

Electricity is caused by the flow of electrons moving through a conducting material

• Those electrons go from the power source to the device
• In the appliance they leave their energy behind
• They go back to the power source to be charged.

Electric wire

The plastic around the wire is an insulator (wire insulation)

The coper wire is a conductor (stripped wire)

Voltage

 Voltage (U) is how much electrical energy each electron is carrying. 

 

Measured in Volts (V) with a voltmeter

Current

A current (I) is how many electrons flow past every second.

 

Measured in Amps (A) with an "ammeter" (amperemeter)

Voltage 

The power outlet has a voltage of 230V 

• This can be dangerous and even deadly

24V is the safe limit  

Transformers raise/lower voltage

Power

Power (P) is the amount of electrical energy used per second by a device.

Measured in Watts (W)

Watts is also J/s (joules per second)

Calculate Power

Power can be calculated with the formula: P = U x I 

P for Power (in W = Watt)

U for Voltage (in V = Volt)

I for current (in A = Ampere)

Energy consumption

All electrical devices use energy  → energy consumption

The amount of energy can be calculated with the formula:  E = P · t

E = Energy (in J = Joules)

P = Power (in W = Watt)

t = time (in s = seconds)

Question 1

A device has a battery of 12V. There is a current going through the devies of 5A. What is the power (P) of this devies?

Calculation 1

A device has a battery of 12V. There is a current going through the devies of 5A. What is the power (P) of this devies?

Answer:

P = U x I

U = 12 V

 I = 5 A

P = 12V x 5A = 60W

Question 2

A telephone has a 15V battery. Its power in low energy mode is 45W.

What is the current in the telephone?

Calculation 2

A telephone has a 15V battery. Its power in low energy mode is 45W.

What is the current in the telephone?

Answer:

P = U x I    -> I = P / U

U = 15 V

P = 45 W

I = P / U = 45W / 15V = 3A

Question 3

An electric kettle using a current of 2,17 A takes 1 minute and 54 seconds to boil the water.

Calculate the energy consumption of the kettle in kJ.

Calculation 3

An electric kettle using a current of 2,17 A takes 1 minute and 54 seconds to boil the water. Calculate the energy consumption of the kettle in kJ.

Answer:

• U = 230 V (from the socket); I = 2,17A
• P = U x I = 230 x 2,17 = 499,1 W  
• t = 60 + 54 = 114 s

E = P x t

E = 499,1 x 114

P = 56 897 J = 56,9 kJ

What is an insulator?

1. A material that does not conduct electricity
2. A material that conducts electricity
3. A clamp to connect two electric wires
4. An electric source

There is a electrical current when...

1. the circuit is closed
2. when there is a electric source
3. when the wires are conductors
4. all three need to be true

Energy

Power

Time

Voltage

Current

I

P

U

E

t

What part of an atom makes it possible for electrical energy to travel?

1. Proton
2. Nucleon
3. Muon
4. Electron

The formula is P = U x I
Which of these is also correct?

1. U = I / P
2. U = P x I
3. U = P / I
4. U = P + I

What is the Voltage of a power outlet in a house?

1. 360 V
2. 12 V
3. 230 V
4. 1500 V

phet.colorado.edu

Assignment 

Make the following circuits work in the app: "Inleiding"

• let a lightbulb burn with a battery
• let a lightbulb burn with a battery and a switch
• let 2 lightbulbs burn with a battery and a switch

Homework

• Read Topic 2.3 (p. 70-73)
• Complete the exercise of Topic 2.3 (p.74-77)
• Study the glossary of Topic 2.3 on StudyGo.