Resistance is a measure of how much a component resists or reduces the flow of electric current. Components with higher resistance allow less current to flow than those with lower resistance. Resistance is calculated by dividing the voltage by the current using the formula: Resistance (R) = Voltage (V) / Current (I). This relationship can be used to determine the resistance of resistors in circuits based on the voltage provided and current flowing.

1. 28 April 2010 Resistance in Circuits Different components draw different amounts of current from the power supply . This is because each component resists the flow of charge differently. A component that allows a big current through has a small resistance. A component that allows a small current through has a big resistance. Resistance is measured in Ohms, 

2. A resistor is a component that resists (slows/reduces) current. There are many sizes of resistor with different resistance values. In a circuit diagram a resistor is shown by: or 4  is the resistance of these resistors. Consider these two circuits: The resistor in circuit is ______ because the current is _________ 2 bigger / smaller bigger / smaller 4  4  2A 4  12V 2A 6  1 12V 4A 2

3. Calculating Resistance: Voltage,V = 12V Current, I = 2A Resistance,R = 6  Is there a relationship between these numbers? 12V 4A 1 2 1 12 2 6 V I R 2A 4  12V 2A 6 

4. V I R =  V I R

5. V I R = V I R

6. V I R = V I R

7. Calculate the resistance of the resistors in these circuits: 3A 3 I= R= V= = = We SIN SU 12V 6A 1 V= I= R= = = 6V 2  2 V= R= I= = = 10V 5A 4 V= I= R= = = 4  9V 3  5 V= R= I= = =