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= = =