9.8 How components affect the current

• Science
• Middelbare school
• vmbo lwoo, vwo
• Leerjaar 2

 9.8 How components affect the current

This lesson

• recap quiz
  
• What is voltage?
• What is resistance?
• Formulas Resistance and voltage

Learning goals

• You can explain what resistance is in your own words.

• You can explain what voltage is in your own words.
  

Know the formula of resistance and do calculations with it.

• You can describe the difference between how current is measured and how voltage is measured.
  

• You can describe how voltage gets divided over series and parallel circuits.

An iPhone charger uses a current of 0.08 ampere when connected to a European socket. With this current it takes an iPhone 12, 2 hours and 8 minutes to go from 0% to 100%. How much coulomb flew through the wire in this time?

1. 576 C
2. 0.224 C
3. 614.5 C
4. 96000 C

A current of 0,6 A flows out of the battery. What is the current flowing through each lamp?

1. 0.2 A
2. 0.6 A
3. 0.3 A
4. 1.2A

A current of 0,6 A flows out of the battery. What is the current flowing through each lamp?

1. 0.2 A
2. 0.6 A
3. 0.3 A
4. 1.2A

Current out battery = current component 1 = current component 2 =....

Series circuits

Current out battery = current branch 1 + current branch 2 +....

Parallel circuits

Resistance & voltage

What is resistance?

Resistance is the opposition to current flow.

What is voltage?

1.A force needed to make the charges flow in a circuit.

(also known as potential difference)

• What is the difference between how you connect an ammeter and a volt meter in a circuit?
  

• How does voltage get divided over series and paralel circuits?

• What is the difference between how you connect an ammeter and a volt meter in a circuit?

An ammeter gets connected in series while a volt meter gets connected parallel.

• How does voltage get divided over series and paralel circuits?
  

	Series	Parallel
Voltage	Gets divided over the components	The same at every circuit loop.

Homework

• Read 9.8 + 9.9
• Do the yellow block exercises of 9.8 and work book
• Do the yellow block exercises of 9.9 and workbook

 the brightness is normal with one lamp

With two lamps:  1. the lamps are dimmer 

2. The value on the ammeter is halved. 

Each component like lamp provides resistance to the flow of charge

What is Resistance: Resistance is the opposition to the flow of charge (electrons)

With two cells 1.the lamp is brighter and the value on the ammeter is twice that it was before.

Parallel circuit with two lamps.

1. Brightness is the same as one lamp.

2.Adding more lamps in parallel increases the current.

Parallel circuit with two cells

The current (I)  in the circuit depends on:

1. Voltage(V)

2. Resistance ( R)

 I = V / R (Current = Voltage Divided by Resistance)

Formulas: resistance and voltage (Ohm's law)

 I = V / R (Current = Voltage Divided by Resistance)

I is current measured in amperes and

V is voltage measured in volts.

R is resistance measured in ohms 

Rearrenging the formula:

     V = I x R (Voltage = Current multiplied by Resistance)

R = V / I (Resistance = Voltage divided by Current)

Resistance

Symbol: R

Unit: Ohm

 Symbol for Ohm: Ω

Resistance is the opposition to current flow.

Examples:

• Resistance = 5 Ohm
  
• R = 5 Ω
  

Exercise 1

Find out the amount of current flowing through the electric heater having a voltage of 220 V and resistance is 10 Ω.

Find out the amount of current flowing through the electric heater having a voltage of 220 V and resistance is 10 Ω.

G:   V= 220 v , R= 10Ω.

A: I =?

F: I= V/R

C:  I= 220/10=22 A

Example 2

Find the resistance of an electrical circuit which has the voltage supply of 10 Volts and current of 0.005 A.

Find the resistance of an electrical circuit which has the voltage supply of 10 Volts and current of 0.005 A.

G: V=10 v    I= 0.005 A

A:  R = ?

F:   R= V/I

C:  R= 10/0.005 = 2000 Ω

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