2. Fill in the gaps for the unknown Voltage and current readingsb) c) d) e)

3. Current & Ammeters Investigation
Place an Ammeter at various point in a circuit with one bulb and measure the current flow
Repeat with two bulbs in series
Repeat with two bulbs in parallel 1. 2.
For each task draw a circuit and record the current values at each point (either side of a light bulb) measured in the circuit. 3.
What can you conclude about
Current in S & P circuits ???

4. What can you conclude about Voltage in S & P circuits ???
Voltage investigation
Investigation:
Set up a circuit with one bulb and measure the Voltage drop across the bulb (V1) and power supply (Vs)
2. Repeat with two bulbs in series, measure V1 V2 and Vs
3. Repeat with two bulbs in parallel, measure V1 V2 and Vs
For each task draw a circuit and record the voltage values for each component, then comment on your observations (ie bulb brightness).
What can you conclude about Voltage in S & P circuits ???

5. Circuit in series
In a series circuit, each device is connected in a manner such that there is only one pathway.

6. The electrons move with the same speed anywhere in the circuit
Current in a series circuit is constant.
I1 = I2

7. It does NOT matter where the current is measured, or where the ammeter is placed
I = I1 = I2
Proved!
Make this circuit and prove the above Theory!

8. Voltage in series circuits
Voltage in a series circuit is shared between the resistances.
That’s why the light bulbs get dimmer when we add another light bulb to the circuit

10. V & I in a (series) circuit

11. I = Vs/R Basic Circuit: Series Circuit: V1 + V2 = VS RT = R1 + R2
Current (I) has the same value everywhere in the circuit
RT = R1 + R2 I
V1 + V2 = VS RT Vs I
I = V/RS

12. Equivalent Series Resistance
12 W a b
4 W
8 W a b

14. What is the series resistance?4
16 V 4
What is the series resistance?
Calculate the current in this circuit.

15. Ex:
47  V
28 
The current through the 47  resistor is 0.12 A Calculate the voltage V of the battery.

16. A V I R The supply voltage is 12 V.
The potential drop across the lamp is 4.0 V
The current I = 3.0 A.
Calculate the resistance R A V I R
The supply voltage = 12 V (A potential rise (PR))
The voltage across the resistor + lamp = 12 V (A potential drop (PD))
The voltage drop across the ammeter is insignificant.
Mathematically 12 V = VR + 4 V
rearranging VR = = 8 V

17. For some Christmas lights, if one bulb is blown, the whole string goes out. For others, one bulb can go out and the rest stay lighted. What is the difference ?

18. Circuits in parallel
In a parallel circuit, each device is placed in its own separate branch.

19. Voltage in parallel circuits
A Voltmeter is always connected in parallel with the component

20. The brightness of the light bulb does NOT change when we add another bulb in parallel

21. Voltage across the light bulb is the same as the voltage in the battery.
V1 = V2
Proved!
Make this circuit and prove the above Theory!

22. Current in parallel circuits
The current is shared through the resistances in a parallel circuit
Make this circuit and
prove the above Theory!
Proved!

23. V & I in a (Parallel) circuit

24. In a series circuit, the current is the same through each resistorV R2
In a series circuit, the current is the same through each resistor R1 V R2
In a parallel circuit, the voltage is the same across each resistor

25. Parallel Circuit: Ic = I1 + I2 VBatt = VR1 = VR2 I1 = V/R1 I2 = V/R2?
I1 = V/R1
I2 = V/R2 RP V I1
Ic = V/RP

26. (RP < R1 , R2)!!! Resistors in Series RS = R1 + R2
Resistors in Parallel R1 R2
(RP < R1 , R2)!!!

27. Equivalent Parallel Resistance
6 W
30 W a b
5 W a b

28. What is the parallel resistance?
16 V 4 4
What is the parallel resistance?
Calculate the current in all branches of this circuit.

29. Ex: V
47 
28 
The current through the 47  resistor is .12 A Calculate the current through the 28  resistor.

31. Circuit solving 13.7 V 3 A R A car battery has a voltage of 13.7 V.
The current I = 3 A.
The resistors are identical.
Calculate the resistance of each resistor (R).
To find the total resistance (RT) of the circuit

32. Excellence The supply voltage is 12 V. The current I = 2.0 A.
The resistors are identical.
Show the resistance of each resistor is 12 Ω
Excellence