1. Electric Potential Energy and Voltage

2. What is voltage?
Potential difference describes the difference in potential energy between two points of an electric circuit.
Potential difference is another name for voltage.
Unit = volt (V)
Measured by a voltmeter
Voltage is what cause charges to move.
The type of energy contained in an electron
is called potential energy
Think of a waterfall - Water naturally flows from higher point to lower .charges naturally move from higher level of energy to lower.
The difference in potential energy between one point in a circuit and another – the voltage – makes charges move in a cirucuit.
WB p , reading voltmeter problems p174

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WB p , reading voltmeter problems p174

6. Intro to Voltage video

7. Measuring Voltage
To measure the voltage across a component in a circuit, you must connect the voltmeter in parallel with it.
You can measure the voltage across a cell or battery.
The more cells, the bigger the voltage.

8. Volt meter measuring voltage of a lamp
Voltage will show decrease

9. Calculating Voltage V = Voltage E = = change in Energy ( in Joules)
Q = amount of charge (in coulombs)

10. Cell in Series – Voltage adds up
Increasing the number of cells in series increases the voltage (equal the sum of the individual cells)
Eg. A 12V led-acid battery of a car is composed of really six 1.5V cells connected in series.

11. Cell in Series
Three 1.5 V electric cells are connected in series to form a battery.
What is the Total Voltage?

12. Cell in Series
Three 1.5 V electric cells are connected in series to form a battery. V t V total = 3 (1.5V)
= 4.5 V

13. Cells in Parallel –Voltage does not increase
When cells are provided in parallel, they DO NOT provide more voltage.
But they do provide a greater amount of charge.
They can provide more charge in a given time (greater current) or provide a given charge for a longer time (longer battery life).

15. Homework
CYU p 314 #1, 3, 4, 5, 7, 8, 10.
WB p , reading voltmeter problems p174
Or other WB p

17. In a SERIES Circuit: VT = V1 + V2 + V3 …. IT = I1 = I2 = I3 ….
Current: same through whole circuit; equal to Total Current
IT = I1 = I2 = I3 ….
Voltage: voltage across loads ADD UP to TOTAL VOLTAGE
VT = V1 + V2 + V3 ….
Resistance: Resistors INCREASE total resistance in circuit  TOTAL CURRENT DECREASES in circuit as resistors are ADDED.
RT = R1 + R2 + R3 ….

18. Current in Series I1 = I2 = IT 0.5 A = 0.5 A = 0.5 A V1 + V2 = VT

19. In Parallel Circuits: IT = I1 +I2 + I3 ….
Current through each path = Total current
IT = I1 +I2 + I3 ….
Voltage: SAME across each load as total voltage
VT = V1 = V2 = V3 ….
Resistance: Resistors DECREASE total resistance in circuit  TOTAL CURRENT INCREASES in circuit as resistors are ADDED.