H5.3a Seriecircuits TV3B

• Natuurkunde
• Middelbare school
• vwo
• Leerjaar 3

5.3a Seriescircuits

Connecting resistors

Last week

• (I,U)-diagram is a graph in which the current is plotted against the voltage.
• A resistor obeys Ohm's law, resistance is always constant.
• A light bulb does not, because the resistance of the filament increases as the wire heats up.

The package of an LED light bulb reads: 12 V/ 100 mA.
Calculate the resistance of the light bulb when it is lit at the correct voltage.

Elaboration:

Given:

U = 12 V

I = 100 mA = 0,100 A

Asked:

R = ?

Elaboration: R =      =              = 120 Ω

​I​​U​​

​0,100​​12​​

This lesson

Lesson goals:

• you know what a series circuits is.
• you can calculate the voltage across each resistor in a series circuit.
• you can calculate the equivalent resistance of the resistors in a series circuit.

Serie circuit

Parallel circuit

Mixed circuit

Serie circuit

Current

• rule: current flows from + to - (elektrons from - to +)
• The current is the same everywhere in a series circuit (because the current can only go through 1 'path')
• I = I₁ = I₂ = I₃ = ...

serie circuits

Voltage

• The voltage divides among the various components in a series circuit.
• Utot = U1 + U2 + ...

serie circuits

Equivalent resistance

• more resistors in an circuit  --> bigger resistance
• R_eq = R1 + R2 + R3 + ...
• R_eq = equivalent resistance = the total resistance in Ω

serie circuits

=

10

Utot = U1 + U2 + ...

I = I1 = I2 = I3 = ...

R3 = U/I = 6/0.12 = 50Ω

R3 = R1 + R2

1,2 V

4,8 V

1,2 V

0,12 A

0,12 A

40

10

=

Circuitry Analysis

1. Simplify all parallel 'blocks'.
2. Calculate Req.
3. Calculate Isource.
4. Calculate the voltage across each 'block'.
5. Calculate the individual current through e.ach resistor

Exercise 

	Resistance (Ω)	Current (A)	Voltage (v)
R1	5000
R2	3300
R3	500
R4	100

Assignement: Complate the table shown on the bottom of this slide. Analyze the circuit according to the instructions given.

R_eq = R1 + R2 + R3 + .....

I_source = I1 = I2 = I3 =.....

U_source = U1 + U2 + U3......

R_eq = R1 + R2 + R3 + R4 = 5000+3300+500+100 = 8900Ω

I_source = U_source/R_eq = 24/8900 = 0,00269

Stap 2: 

R_eq

Stap 3:

I_source

Stap 4: 

U1...

U = I x R

U1 = 0,00269 x 5000 = 13,5 V

U2 = 0,00269 x 3300 = 8,9 V

U3 = 0,00269 x 500 = 1,35 V

U4 = 0,00269 x 100 = 0,27 V

Summary

• Current is the same everywhere in series circuit.
• The voltage distributes itself among the various components
• Equivalent resistance (R_eq) can be calculated by adding the resistances together.

Individuel assignment

Stap 2:

Calculate R_eq

Stap 3:

Calculate I_source

Stap 4:

Calculate the voltage across each 'block'.

	Resistance (Ω)	Current (A)	Voltage (V)
R1	2000
R2	1470
R3	2200
R4	1850

Rtot = R1 + R2 + R3 + .....

Ibron = I1 = I2 = I3 =.....

Ubron = U1 + U2 + U3......

Homework: 1, 3, 4 

Questions? Send in the chat or put your mic on. 

Individuele Assignment

Homework

5.3:  3ab, 4, 5, 6