6-4 Bodily resistance and resistance in series (6.2)

• Natuurkunde
• Middelbare school
• havo
• Leerjaar 3

Bodily resistance and resistance in series (p 228)

Stationary

- Writingbook

- Pen and pencil

- Calculator

- iPad

Mark

- NO

Lessonup

- YES

schoolbag in

the cupboard

Phones in the phonebag

Lesson goals:

- Explain how bodily resistance 

influences the current through 

your body during an electric shock.

- Make calculations with the current,

voltage and resistance in a series circuit.

Size of the current?

- Depends on the voltage and

resistance.

- Total bodily resistace =

contact resistance + body resistance

Body as a conductor

- The body is a good conductor

- Body resistance is between 100 and 500 ohm

- Contact resistance is about 100 k ohm if your skin is dry

- With a wet skin - drops to 1 000 ohm

Correct voltage for the perfect lightbulb

A lightbulb that works perfectly

at 6V could be damaged at 9V.

Say you have a battery of 9V, 

but a lightbulb of 6V, could you then still conenct the lightbulb to this battery?

6V lamp and 9V powersource

Then you have to increase the resistacne 

to use the 9V battery.

BECAUSE - If the resistance increases, the current will decrease.

More resistances in series

The more resistances you connect in sereis the greater the total resistance will be. Rtot = R1 + R2 + R3

SO Rtot = 250 + 550 + 1 000 = 1 800 ohm

Total resistance

Current and voltage in a series circuit 

The current in a series circuit

is the same everywhere...

.... BUT the voltage is shared

accrosst he circuit components

What if the resistance are different ...

U​1​​=I⋅R​1​​

U​2​​=I⋅R​2​​

U​3​​=I⋅R​3​​

R​1​​

R​2​​

R​3​​

What is the total resistance?

1. 9
2. 3
3. 12
4. 11

How does the
current at A1 compare to the current at A2?

DIRECTION OF CURRENT

1. A1 > A2
2. A1 = A2
3. A1 < A2
4. One could not say

What is the voltage in U2?

1. 3V
2. 6V
3. 9V
4. 12V

What is the voltage in U?

1. 3V
2. 6V
3. 9V
4. 12V

What is the
current?

1. 2 A
2. 3A
3. 5 A
4. 1,2 A

What is the current?

1. 7 A
2. 4 A
3. 3 A
4. 1,2 A

What is the
magnitude of the
unknown resistance?

1. 1
2. 2
3. 3
4. 4

Do question 27 (p 238)

Do question 28 (p 238)

Do question 29 (p 238)

What did you
learn today?

You could do Q 22 and 23 in the digital method (p 231)

This is on bodily resistance

NEXT LESSON - Parallel circuits