# 6-3 Law of ohm (6.2 p 226)

Law of ohm (p 226)

Stationary
- Writing book
- Pen, pencil
- Calcualtor

Mark
- NO

Lessonup
- YES
Schoolbags in
the cupboard
Phones in the phone bag
1 / 18
Slide 1: Tekstslide
NatuurkundeMiddelbare schoolhavoLeerjaar 3

In deze les zitten 18 slides, met interactieve quizzen en tekstslides.

Lesduur is: 50 min

## Onderdelen in deze les

Law of ohm (p 226)

Stationary
- Writing book
- Pen, pencil
- Calcualtor

Mark
- NO

Lessonup
- YES
Schoolbags in
the cupboard
Phones in the phone bag

#### Slide 1 -Tekstslide

Lesson goals:
• Give ohms law in words and
in a formula.
• Draw graphs showing conductors adhering to ohms law and conductors that dont adhere to ohms law.
• Explain what an NTC and LDR is
And then you will do a practical where you draw graphs of a lightbulb and a resistor.

#### Slide 2 -Tekstslide

Ohm's law
The voltage across a conductor and the current through a conductor are directly proportional if the resistance remains constant.

#### Slide 3 -Tekstslide

Direct proportionality

As one amount increases, the other amount increases at the same rate.

#### Slide 4 -Tekstslide

What is the relationship between voltage and current?
A
Linear relationship
B
Directly proportional
C
Inversely proportional
D
Proportional relationship

#### Slide 6 -Quizvraag

What is the relationship between the current and the resistance?
A
Linear relationship
B
Directly proportional
C
Inversely proportional
D
Proportional

#### Slide 7 -Quizvraag

What is the unit for voltage?
A
Ampere
B
Volt
C
Ohm
D
Kilogram

#### Slide 8 -Quizvraag

The resistance in a circuit remains constant. At a voltage of 1,7 V the current is 3,5 A. What is then the current at a voltage of 5,1 V?
A
1,2 A
B
2,5 A
C
8,3 A
D
10.5 A

#### Slide 9 -Quizvraag

The resistance in a circuit remains constant. At a voltage of 1,7 V the current is 3,5 A. What is then the voltage at a current of 5,6 A?
A
1,1 V
B
2,7 V
C
2,9 V
D
3,2 V

#### Slide 10 -Quizvraag

Explain what a direct proportionality is.

#### Slide 11 -Open vraag

NTC - negative temperature coefficient
An NTC is sensitive to changes in temperature. If the temperature rises the resistance decreases.

Uses: prevents overheating in electronic
appliances like computers and
amplifiers.

#### Slide 12 -Tekstslide

LDR - Light dependent resistor
Sensitive to changes in light. More light results in less resistance.

Uses: As a switch in a nightlamp

#### Slide 13 -Tekstslide

An NTC is sensitive to changes in
A
temperature
B
light
C
current
D
voltage

#### Slide 14 -Quizvraag

Now do experiment 2 and 3 (p247 and 248)

Rules:
- Work in groups of 2 or 3
- It is not for a mark.
- Important to have the graph of U vs I
for the lightbulb and the resistor done
in 20 minutes.
timer
20:00

#### Slide 15 -Tekstslide

Resistance and temperature
With an incandescent lightbulb
there is a deviation from the
direct proportionality.

The reason is the high temperature of
the filament. The higher the temperature
the greater the resistance.

What did you
learn today?

#### Slide 17 -Woordweb

Homework
Test yourself 6.2