Lesson 7 — 5.3 Series and parallel

This lesson
  • Recap questions
  • Resistance, voltage & current — Parallel and series
  • Working on exercises.
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This lesson contains 11 slides, with interactive quiz and text slides.

time-iconLesson duration is: 45 min

Items in this lesson

This lesson
  • Recap questions
  • Resistance, voltage & current — Parallel and series
  • Working on exercises.

Slide 1 - Slide

A electrician is working on a series circuit with a current of 0,83 A flowing through it and a total resistance of 8 Ω. He adds two resistors of 4 Ω each to this circuit. After this he doubles the voltage over the circuit.

What will happen to the current flowing through the circuit after this?
A
You can't tell because you aren't given the voltage over the circuit.
B
It wil double.
C
It will be half as much
D
It will be the same.

Slide 2 - Quiz

 A physicist wants to make a charge of 6,4∙10^-15 C flow through a wire. He knows the resistance of the wire is 25 Ω. He applies a voltage of 8 V over the wire. How long does a current have to flow through the wire to let the required amount of charge flow through it?

Slide 3 - Slide

 A physicist wants to make a charge of 6,4∙10^-15 C flow through a wire. He knows the resistance of the wire is 25 Ω. He applies a voltage of 8 V over the wire. How long does a current have to flow through the wire to let the required amount of charge flow through it?
Given:
- Required amount of charge: 6,4 • 10^15
- R = 25 Ω
- U = 8 V

Asked:
How long does current have to flow through the write to reach the required amount of charge?

Working:
R = U/I                   I = U/R

Q = I • t                  t = Q/ I

I = 8/ 25 = 0.32 A
t = (6,4 • 10^15)/ 0,32 = 2 • 10^16 seconds

Slide 4 - Slide

Different types of resistors
  • What is an ohmic resistor?
  •  What material can be used to make an ohmic resistor?
  • Why do other materials not follow Ohms law?
  • What does NTC stand for?
  • What is the relationship between temperature and resistance in an NTC?
  • What would the opposite of an NTC be called?
  • What doe LDR stand for?
  • What is the relationship between light and resistance in an LDR?

Slide 5 - Slide

Different types of resistors
What is an ohmic resistor?
  • A resistor where the resistance is the same regardless of the voltage.

 What material can be used to make an ohmic resistor?
  • Constantan

Why do other materials not follow Ohms law?
  • An increase in voltage causes an increase in current in a circuit. This increases the temperature of the wire. This causes the resistance to increase.

Slide 6 - Slide

Different types of resistors
What does NTC stand for?
  • Negative temperature coefficient. 

What is the relationship between temperature and resistance in an NTC?
  • An increase in temperature causes a decrease in resistance and vice versa.

What would the opposite of an NTC be called?
  • A PTC — Positive Temperature Coefficient.

What doe LDR stand for?
  • Light dependent resistor.

What is the relationship between light and resistance in an LDR?
  • If more light falls on the reistor its resistance will decrease and vice versa.

Slide 7 - Slide

Resistance, voltage & current 

Series and parallel


Equivalent resistance

Slide 8 - Slide

Resistance, voltage & current — Series circuit
Resistors in series


Voltage in series


Current in series


Rtot=R1+R2+R3+...
Utot=U1+U2+U3...
Itot=I1=I2=I3=...

Slide 9 - Slide

Resistance, voltage & current — Parallel circuit
Resistors in series


Voltage in series

Current in series


R1tot=R11+R12+R13+...
Itot=I1+I2+I3=...
Utot=U1=U2=U3=...

Slide 10 - Slide

Homework
Exercise:
< 1, 2, 3, 4, 5, 7
> 3, 4, 7, 8, 9, 10

Slide 11 - Slide