1. WARM UP
Draw a picture of a SERIES Circuit. Show a battery, a switch, and a light bulb in your drawing.
Draw a picture of a PARALLEL Circuit. Show a battery, a switch, and TWO light bulbs in your drawing.
Be prepared to discuss your pictures.

2. Ohm’s Law

3. What is Ohm’s Law?
The law stating that the direct current flowing in a conductor is directly proportional to the potential difference between its ends.

4. Ohm’s Law

5. The Resistance is halved!
What Happens?
What happens to the Resistance when the Current is doubled and the Voltage stays the same?
The Resistance is halved!

6. The Voltage is Tripled too!
What Happens?
What will happen to the Voltage when the Resistance is tripled and the Current remains constant?
The Voltage is Tripled too!

7. What Happens?
What happens to the Current when the Resistance is reduced by 1/3 and the Voltage stays the same?
The Current is Tripled!

8. Measuring Current Current is measured in units of amperes (A)
In a series circuit, current is the same at all the points
In a parallel circuit, current is shared between all the points

9. What is the current? SERIES CIRCUIT PARALLEL CIRCUIT 3A 3A 4A 1A 4A 1A

10. Measuring Voltage
Voltage – the electrical push that a cell/battery gives to the current
Voltage is also known as Potential Difference
Voltage is measured in units of volts (V)

11. Measuring Voltage 3V
1.5V 3V
In a series circuit, voltage is shared between all the points
In a parallel circuit, voltage is the same at all the points

12. What is the current and voltage?
Series
Same
Shared
Parallel

13. What is the current and voltage?

14. In a series circuit, add up all resistance to get the total.
Measuring Resistance
Resistance – slows down current, adding components to a circuit increases resistance
Resistance is measured in units of ohms (Ω)
More resistance = Less current = Less light
In a series circuit, add up all resistance to get the total.

15. QUESTION Use the OHM’s Law Equation to answer this question:
What happens to the Resistance when the Current is tripled and the Voltage stays the same?

16. QUESTION Use the OHM’s Law Equation to answer this question:
What happens to the Voltage when the Resistance is reduced by 1/2 and the Current stays the same?

17. What is Electrical Power?
Electric power is the rate, per unit time, at which electrical energy is transferred by an electric circuit.
The SI unit of power is the watt [W], one joule per second, [ J/s].
Electric power is usually produced by electric generators, but can also be supplied by sources such as electric batteries.

18. Electrical Power

19. How much voltage gives 5 amps of current through a 3 Ω light bulb?
I = V/R
V = (5A)  (3Ω)
V = 15V

20. How much current flows in a circuit with a 1
How much current flows in a circuit with a 1.5 volt battery and three 1 ohm resistances (bulbs) in series?
I = V/R
I = (1.5V) / (3Ω)
I = .5A

21. What is the voltage drop across each resistor in the circuit?
In a series circuit, voltage is shared between all the points
9V/3 = 3V

22. P = IV I = V/R I = (1.5V) / (1.5Ω) I = 1A P = (1A)  (1.5V) = 1.5 W
A light bulb with a resistance of 1.5Ω is connected to a 1.5V battery in the circuit. Calculate the power used by the light bulb?
P = IV
I = V/R
I = (1.5V) / (1.5Ω)
I = 1A
P = (1A)  (1.5V) = 1.5 W
P = 1.5 W