Resistors

Resistors & Resistance

• Looking at the top resistor the first band is green,

• Looking at the top resistor the first band is green,

• If we look at the first band column we can see green = 5

• Looking at the top resistor the first band is green,

• If we look at the first band column we can see green = 5

• the second band is blue and blue = 6 so we now have 56

• Looking at the top resistor the first band is green,

• If we look at the first band column we can see green = 5

• the second band is blue and blue = 6 so we now have 56

• as this is a 4 band resistor there is no 3rd band instead we move to the multiplier band

• If we look at the bottom resistor it is a 5 band resistor so we will use the 3rd column

• If we look at the bottom resistor it is a 5 band resistor so we will use the 3rd column

• Red = 2 Orange = 3 Violet = 7 the multiplier is black x1 or black is zero so there are NO zeros after the number

• If we look at the bottom resistor it is a 5 band resistor so we will use the 3rd column

• Red = 2 Orange = 3 Violet = 7 the multiplier is black x1 or black is zero so there are NO zeros after the number

• so it's 237Ohms 

• If we look at the bottom resistor it is a 5 band resistor so we will use the 3rd column

• Red = 2 Orange = 3 Violet = 7 the multiplier is black x1 or black is zero so there are NO zeros after the number

• so it's 237Ohms

• The last band on both resistors is the tolerance band

• The tolerance band tells us how accurate the resistor is

• The tolerance band tells us how accurate the resistor is

• the band on the top resistor is GOLD = +/- 5%

• The tolerance band tells us how accurate the resistor is

• the band on the top resistor is GOLD = +/- 5%

• meaning a 100Ohm Resistor could measure between 95 - 105 Ohms

Fill in the Blanks

Fill in the Blanks

Multiple Choice

What is the tolerance of this resistor

• 10%

• 5%

• 1%

• 0.5%

Multiple Choice

What Colours would a 1.2MOhm resistor have? (1200000 Ohms)

• Brown, blue, yellow

• Brown, black, red

• Brown, red, green,

• Red, Yellow, Pink

Resistors In Series

When Resistors are in series the electrons have to pass through all the resistors in the circuit,
each resistor adds more resistance as the electrons travel through, we can calculate the total resistance like this...

​In this example 3K, 10K and 5K add up to 18K Ohms, with this calculation we can unlock more information.

​​Total Resistance

​We can see the circuit is powered by 9 Volts. We can now use ohms law to find the current.

​​Total Current

​With our current we can now use Ohms law to find out the Voltage Drop across each resistance

​​Voltage Drop

​Your 3 voltage drops Will add up to your supply voltage, circuits always drop their supply voltage across their components.

​​Kirchhoff's Law

Multiple Choice

Under Kirchhoff's Voltage Law what is the missing Voltage Drop?

0V = 24V - 12Vd1 - ??Vd2 - 7Vd3

• 8Vd2

• 12Vd2

• 7Vd2

• 24Vd2

​With our Current of 0.0012A or 1.2mA we can now calculate our voltage drops...

0.0012A x 5000 Ohms = 6Vd1
0.0012A x 10000 Ohms = 12Vd2

So while the resistors drop voltage the Batteries gain Voltage and looks like this...

0=12V1 - 6Vd1 + 6V2 - 12Vd2

All component drops and gains equate to Zero.